feat(typechecker): carrier-aware Echo gate — float locals soundly reject (ADR-0010)

Closes the float-locals soundness gap flagged in ADR-0010: the Safe-only reverse
gate now consults the carrier of the target variable, including float LOCALS.

The Echo admissibility check runs at the reverse-block site inside
check_control_stmt, where self.env already holds the INFERRED types of params
and prior local assignments (locals carry no annotation, but `x = 2.5` records
x : Float in the env). So check_echo_admissible / check_echo_admissible_with_residue
now build a CarrierEnv from self.env (numeric Type -> BasicType; non-numeric and
not-yet-inferred Any omitted -> default Int = Safe) and classify via
echo::classify_stmts_in_env.

Effect:
  * `reverse { x += v }` over a float local (or param) is correctly REJECTED
    under Safe-only -- float reverse-add is lossy (Neutral), was wrongly
    Safe-admitted before.
  * `reversible { x += v } -> tok` over a float still ADMITTED -- the token
    retains the rounding residue (Neutral admissible with residue).
  * int/rational/complex/symbolic/hex/binary unchanged (Safe).

Contained change: no reordering, no new inference pass -- the inferred type env
is already populated at the gate. 4 typechecker tests (float carrier rejected;
inferred-float-local rejected end-to-end; int contrast ok; float reversible-tok
admitted). Whole-suite check: nothing relied on float reverse{} being accepted,
so the stricter rule breaks no existing test/example.

ADR-0010 + STATE.a2ml updated: slice landed; remaining minor corner noted
(carrier-awareness inside reversible-if branches).

cargo fmt + clippy clean; 127 lib tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BJmfoz1ZS1Pejy9LLMY742

Author: claude

.machine_readable/6a2/STATE.a2ml

@@ -7,7 +7,7 @@ project = "julia-the-viper"
 version = "0.0.1"
 last-updated = "2026-06-18"
 status = "active"
-session = "2026-06-18 — Echo arc completed + number systems stratified. (b) Echo+Epistemic first-class DONE (proof side, ADR-0009): JtvEcho.lean SECTION 5 = Epistemic lattice + Echo×Epistemic product FunctionEffect lattice + comm/assoc/idem composition laws (matching the already-merged echo.rs/epistemic.rs/effect.rs). Number systems STRATIFIED (ADR-0007 D6 realized as ADR-0010): JtvEcho.lean SECTION 6 3-level NumAlgebra tower 1:1 with the Echo lattice (hex/binary=ℤ-encodings collapse to int's tier; float=approxGroup→Neutral); echo.rs carrier-aware classification (CarrierEnv; reversible += graded shape⊔carrier; default-carrier=Int sound) + effect.rs param-seeded env; number.rs runtime-value bridge Value::reversal_echo. PR #44 merged (rebase); bridge+ADR-0010 PR next. lake + cargo green (124 lib tests, 0 sorry/unwrap). NEXT rung: float-LOCALS soundness slice (thread typechecker inferred types into CarrierEnv) + value-level semantics (gap-005)"
+session = "2026-06-18 — Echo arc completed + number systems stratified. (b) Echo+Epistemic first-class DONE (proof side, ADR-0009): JtvEcho.lean SECTION 5 = Epistemic lattice + Echo×Epistemic product FunctionEffect lattice + comm/assoc/idem composition laws (matching the already-merged echo.rs/epistemic.rs/effect.rs). Number systems STRATIFIED (ADR-0007 D6 realized as ADR-0010): JtvEcho.lean SECTION 6 3-level NumAlgebra tower 1:1 with the Echo lattice (hex/binary=ℤ-encodings collapse to int's tier; float=approxGroup→Neutral); echo.rs carrier-aware classification (CarrierEnv; reversible += graded shape⊔carrier; default-carrier=Int sound) + effect.rs param-seeded env; number.rs runtime-value bridge Value::reversal_echo. PR #44 + #45 (bridge+ADR-0010) merged; float-LOCALS soundness gate also LANDED (typechecker.rs check_echo_admissible{,_with_residue} seed CarrierEnv from the inferred env self.env → reverse{} over a float local correctly rejected, float routes to reversible{}->tok). lake + cargo green (127 lib tests, 0 sorry/unwrap). NEXT rung: value-level semantics beyond τ=int (gap-005)"
 
 [project-context]
 name = "Julia The Viper"
@@ -50,14 +50,14 @@ issues = [
   { id = "gap-002", description = "typing_coercion in JtvTypes.lean weaker than docstring — proves existence not coercion to target type", severity = "low", status = "known", follow-up = "ADR needed" },
   { id = "gap-003", description = "Coprocessor implementation gated on PataCL Phase 1", severity = "medium", status = "external-dependency" },
   { id = "gap-004", description = "Reversibility round-trip not guaranteed end-to-end at integration level", severity = "medium", status = "known" },
-  { id = "gap-005", description = "Semantic model is Int-only: the 7 number systems are typed but stated-unproven at the value level; type_preservation mechanised only for τ=int (see ADR-0007 D6 + PROOF-CAPABILITY-MATRIX.adoc). PARTIAL 2026-06-18 (ADR-0010): per-system additive-algebra → Echo-tier CLASSIFICATION now landed at proof/type/value level (JtvEcho SECTION 6, echo.rs carrier_echo, number.rs Value::reversal_echo); the remaining open half is the type_preservation/round-trip SEMANTICS beyond τ=int", severity = "medium", status = "known", follow-up = "value-level semantics for τ≠int; float-locals CarrierEnv inference slice" },
+  { id = "gap-005", description = "Semantic model is Int-only: the 7 number systems are typed but stated-unproven at the value level; type_preservation mechanised only for τ=int (see ADR-0007 D6 + PROOF-CAPABILITY-MATRIX.adoc). PARTIAL 2026-06-18 (ADR-0010): per-system additive-algebra → Echo-tier CLASSIFICATION now landed at proof/type/value level (JtvEcho SECTION 6, echo.rs carrier_echo, number.rs Value::reversal_echo); the remaining open half is the type_preservation/round-trip SEMANTICS beyond τ=int", severity = "medium", status = "known", follow-up = "value-level semantics for τ≠int (the float-locals CarrierEnv inference gate landed 2026-06-18)" },
   { id = "gap-006", description = "RESOLVED 2026-06-15: license decision = MPL-2.0 (code) + CC-BY-SA-4.0 (docs), full per-file. 75 doc headers -> CC-BY-SA-4.0; code stragglers (3 PMPL-1.0 workflows, MPL-2.0-or-later, PLMP/GPL typos, and a deliberate MIT-OR-GPL-3.0-or-later-OR-Palimpsest tri-license on formatter/repl/rsr_check) -> MPL-2.0; PALIMPSEST.adoc (both copies) retired; LICENSING.md rewritten; PMPL badges replaced. Follow-ups: populate LICENSES/ with canonical MPL-2.0 + CC-BY-SA-4.0 texts; add SPDX headers to ~49 header-less docs.", severity = "low", status = "resolved", follow-up = "LICENSES/ texts + header-less docs" }
 ]
 
 [critical-next-actions]
 actions = [
   "Governance hardening (branch claude/jtv-governance-hardening): pin governance-reusable@main → SHA (consistent with sibling standards reusables); add secret-scanner.yml wrapper (standards reusable exists at 524523c); add 'actions' language to codeql.yml; harden proof-regression download-then-run; NOTE the reusable-call-job missing-timeout Hypatia findings are false-positives (timeout-minutes is invalid on reusable-call jobs)",
-  "Number-system stratification (ADR-0007 D6 / ADR-0010) — LANDED 2026-06-18: per-system additive-algebra → Echo-tier classification at proof level (JtvEcho.lean SECTION 6), type level (echo.rs carrier_echo + CarrierEnv carrier-aware += grading, effect.rs param-seeded env) and value level (number.rs Value::reversal_echo). STILL OPEN: (a) thread typechecker INFERRED types into CarrierEnv so float LOCALS grade Neutral — param-only today, so a reverse{} over a float local is wrongly Safe-admitted (soundness slice, NEXT); (b) lift type_preservation semantics beyond τ=int (gap-005); keep addition-only (×/÷ generated)",
+  "Number-system stratification (ADR-0007 D6 / ADR-0010) — LANDED 2026-06-18: per-system additive-algebra → Echo-tier classification at proof level (JtvEcho.lean SECTION 6), type level (echo.rs carrier_echo + CarrierEnv carrier-aware += grading, effect.rs param-seeded env), value level (number.rs Value::reversal_echo), and the carrier-aware TYPECHECKER GATE (typechecker.rs check_echo_admissible{,_with_residue} seed CarrierEnv from the inferred env self.env → reverse{} over a float LOCAL correctly rejected; float routes to reversible{}->tok). STILL OPEN: lift type_preservation semantics beyond τ=int (gap-005); carrier-awareness inside reversible-if branches (rare corner); keep addition-only (×/÷ generated)",
   "v2 (c) token/residue neutral-reversal bridge — LANDED 2026-06-15 (ADR-0007 D5 Neutral tier): JtvEcho admissibleWithResidue + blockEcho_admissibleWithResidue; JtvTheorems execBackwardWithToken + rev_forward_backward_with_token + rev_backward_naive_fails_self_ref; echo.rs self-ref Breaking->Neutral; typechecker.rs check_echo_admissible_with_residue (token unlocks Neutral); reversible.rs RecordedOp::Snapshot residue. NEXT: (b) Echo as a first-class function effect",
   "Echo as first-class function effect ('(b)') — LANDED 2026-06-18 (ADR-0009): echo.rs function_echo + epistemic.rs function_epistemic + effect.rs FunctionEffect row + resolved_effects call-graph fixpoint; JtvEcho.lean SECTION 5 mechanises the Echo×Epistemic product lattice + comm/assoc/idem composition laws",
   "Verification bridge: correlation tests between Lean semantics and Rust interpreter",
@@ -87,7 +87,8 @@ sessions = [
   { date = "2026-06-15", subject = "v2 (c) Neutral reversal bridge LANDED (Lean + Rust). Lean: JtvTheorems execBackwardWithToken + rev_forward_backward_with_token (full-state Bennett recovery, unconditional even for self-referential x += x) + rev_backward_naive_fails_self_ref (token necessary); JtvEcho admissibleWithResidue + blockEcho_admissibleWithResidue + admissible_implies_admissibleWithResidue + neutral_residue_only. Rust: echo.rs reclassifies self-reference Breaking->Neutral (token-recoverable, not erasure; Breaking reserved for future non-group/tropical systems per D6); typechecker.rs splits the Echo gate — reversible{}->tok uses check_echo_admissible_with_residue (admits Neutral; tokenless + reverse{} stay Safe-only); reversible.rs RecordedOp::Snapshot records/restores the residue. lake build + cargo test (99 lib + integration) + clippy -D warnings all green." },
   { date = "2026-06-17", subject = "License + hardening + ADR-0008. License (gap-006 RESOLVED, PR #36 merged): full per-file SPDX = MPL-2.0 (code) + CC-BY-SA-4.0 (docs); 190 MPL + 77 CC-BY-SA headers; PALIMPSEST.adoc retired; LICENSING.md rewritten; stray MIT/GPL/PMPL/or-later normalised. (PR #34 security clean + #35 v2-c bridge also merged earlier.) Workflow hardening (PR #37 merged): curl|sh installers (proof-regression elan, setup.sh just) -> download-then-run; rsr_check.rs unsafe_block self-trip cleared. Deferred (need hyperpolymath/standards reusable, out of session MCP scope): secret-scanner.yml, scorecard.yml job-perms. ADR-0008 (this commit): neg -> reverse-only; purist/adulterated dialect via feature-gated sugar + discouragement lint + purity certificate (resolves ADR-0007 D2); implementation is follow-on." },
   { date = "2026-06-18", subject = "neg-dialect impl slice 1 + ADR-0009. PR #39 merged: jtv-core dialect.rs purity certificate (ADR-0008 D4) -- read-only AST scan stamping a program purist-jtv vs adulterated-jtv by counting expression-level neg sugar; reverse-block subtraction stays purist; 5 tests; cleared a self-introduced Hypatia unwrap_dangerous_default critical via Option::iter().sum(). ADR-0009 (this commit): Echo + Epistemic as first-class GRADED FUNCTION EFFECTS -- Echo grade {Safe<=Neutral<=Breaking} carried in the arrow, composing by the existing join; Epistemic = knowledge/observability axis {Opaque<=Partial<=Transparent} as a parallel graded effect (dual to Echo: loss vs revelation); product-lattice effect row; orthogonal to Purity + the dialect certificate. Implementation slice-wise (Echo-effect first). Still parked: (b) impl, number-system semantics, license wave-2, standards-blocked hardening (secret-scanner/scorecard)." },
-  { date = "2026-06-18", subject = "Echo arc completed + number-system stratification (PR #44 merged via rebase → main: SECTION 5+6 + carrier-aware echo; then bridge+ADR-0010 PR). (b) Echo+Epistemic first-class DONE on the proof side: JtvEcho.lean SECTION 5 = Epistemic lattice (hidden/bounded/full) + Echo×Epistemic product FunctionEffect lattice + comm/assoc/idem composition laws (mirrors the already-merged echo.rs/epistemic.rs/effect.rs). Number systems STRATIFIED (ADR-0007 D6 realized as ADR-0010): JtvEcho.lean SECTION 6 = 3-level NumAlgebra tower (abelianGroup/approxGroup/nonGroup) 1:1 with the Echo lattice; theorems hex_binary_collapse (hex/binary are ℤ-encodings, share int's tier) / exact_groups_safe / float_not_safe (IEEE-754 non-associative → approxGroup → Neutral) / no_current_system_breaks / reversal_tier_by_algebra. echo.rs made carrier-aware: NumAlgebra/additive_algebra/carrier_echo + CarrierEnv threaded through classify_*_in_env/function_echo_in_env; a reversible += is graded shape⊔carrier (float += → Neutral); shape-only wrappers preserve prior behaviour (empty env ⇒ Int=Safe); default-carrier=Int is sound (literals default to int). effect.rs own_effect seeds the env from param annotations. number.rs runtime-value bridge Value::number_system + Value::reversal_echo (delegates to carrier_echo — single source of truth). ADR-0010 reconciles with ADR-0007 D6 (float is approxGroup not D6-cancellative; D6's cancellative/idempotent Neutral/Breaking routes anticipated-but-uninhabited). lake + cargo fmt/clippy/test green (124 lib tests), 0 sorry/admit/axiom, no unwrap/unwrap_or. OPEN: float-LOCALS soundness slice (locals carry no annotation → thread typechecker inferred types into CarrierEnv, else a reverse{} over a float local is wrongly Safe-admitted); value-level type_preservation beyond τ=int (gap-005)." }
+  { date = "2026-06-18", subject = "Echo arc completed + number-system stratification (PR #44 merged via rebase → main: SECTION 5+6 + carrier-aware echo; then bridge+ADR-0010 PR). (b) Echo+Epistemic first-class DONE on the proof side: JtvEcho.lean SECTION 5 = Epistemic lattice (hidden/bounded/full) + Echo×Epistemic product FunctionEffect lattice + comm/assoc/idem composition laws (mirrors the already-merged echo.rs/epistemic.rs/effect.rs). Number systems STRATIFIED (ADR-0007 D6 realized as ADR-0010): JtvEcho.lean SECTION 6 = 3-level NumAlgebra tower (abelianGroup/approxGroup/nonGroup) 1:1 with the Echo lattice; theorems hex_binary_collapse (hex/binary are ℤ-encodings, share int's tier) / exact_groups_safe / float_not_safe (IEEE-754 non-associative → approxGroup → Neutral) / no_current_system_breaks / reversal_tier_by_algebra. echo.rs made carrier-aware: NumAlgebra/additive_algebra/carrier_echo + CarrierEnv threaded through classify_*_in_env/function_echo_in_env; a reversible += is graded shape⊔carrier (float += → Neutral); shape-only wrappers preserve prior behaviour (empty env ⇒ Int=Safe); default-carrier=Int is sound (literals default to int). effect.rs own_effect seeds the env from param annotations. number.rs runtime-value bridge Value::number_system + Value::reversal_echo (delegates to carrier_echo — single source of truth). ADR-0010 reconciles with ADR-0007 D6 (float is approxGroup not D6-cancellative; D6's cancellative/idempotent Neutral/Breaking routes anticipated-but-uninhabited). lake + cargo fmt/clippy/test green (124 lib tests), 0 sorry/admit/axiom, no unwrap/unwrap_or. OPEN: float-LOCALS soundness slice (locals carry no annotation → thread typechecker inferred types into CarrierEnv, else a reverse{} over a float local is wrongly Safe-admitted); value-level type_preservation beyond τ=int (gap-005)." },
+  { date = "2026-06-18", subject = "Float-locals soundness slice (typechecker carrier-aware gate). Echo admissibility is checked at the reverse-block site inside check_control_stmt, where self.env already holds the INFERRED types of params + prior local assignments — so typechecker.rs check_echo_admissible{,_with_residue} now build a CarrierEnv from self.env (Type→BasicType for the 7 numeric Types; non-numeric/Any omitted → default Int=Safe) and call echo::classify_stmts_in_env. Effect: a reverse{} over a float LOCAL (typed only by inference, e.g. x = 2.5) is correctly REJECTED under Safe-only (was wrongly Safe-admitted); reversible{}->tok still admits it (token retains the rounding residue). Contained change (no reordering, no new inference pass). 4 typechecker tests (float carrier rejected; inferred-float-local rejected end-to-end; int contrast ok; float reversible-tok admitted). ADR-0010 §Status/§Consequences/§Open updated (slice landed; remaining minor corner = carrier-awareness inside reversible-if branches). cargo fmt/clippy/test green (127 lib tests; cleared a clippy approx_constant deny on a 3.14 literal → 2.5). Whole-suite check: no existing test/example relied on a float reverse{} being accepted, so the stricter rule broke nothing." }
 ]
 
 [design-artefact-locations]