chore(state): mark Package 4 step 6 closed + record type_info test-fixture drift

Updates STATE.a2ml's Package 4 close-out entry:
- Step 6 no longer 'open/blocked' — landed as 1b32576.
- New pre-existing follow-up recorded: cargo check --all-targets has 4
  test binaries failing to compile because echidna::core::{Hypothesis,
  Definition,Variable} gained a type_info field that the test fixtures
  don't supply. Independent of Package 4, needs separate fix pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.machine_readable/6a2/STATE.a2ml

@@ -692,8 +692,9 @@ commits = [
 pkg-4-shared-types = "Rust workspace now has crates/echidna-core exporting Term, Goal, ProofState, Tactic, Theorem as the canonical shared-types layer. vcl-ut re-exports via vcltotal-interface. No duplication — one canonical source."
 pkg-4-transport = "vcltotal-echidna-client ships as an async REST client keyed to echidna's REST surface (port 8000). Wiremock round-trip tests cover /api/verify, /api/prove, exchange endpoints (/api/exchange/opentheory, /api/exchange/dedukti). 5 round-trip tests green."
 pkg-4-matrix-ci = "backend-matrix.yml runs 113 jobs (one per ProverKind variant) with max-parallel=3. Prep job parses echidna's .machine_readable/provers.a2ml at runtime to emit matrix JSON as an ephemeral GHA output — no committed JSON per the 'no JSON emit' estate rule. Today each job runs the same wiremock suite; when REST surface expands beyond its current 17-prover subset, jobs can diverge per slug without restructuring."
+pkg-4-step-6-closed = "1b32576 feat(rest): /proofs/{id}/export + /exchange/import (OpenTheory + Dedukti). Landed 2026-04-24 after audit confirmed Session C's 'FfiProverBackend breakage' blocker was phantom — cargo check --lib clean on HEAD, every echidna::exchange::* import resolved."
+
 pkg-4-open-followups = [
-  "echidna REST endpoints on HEAD: src/interfaces/rest/{handlers,main,models}.rs have Session C's export/import wiring but are blocked on a pre-existing FfiProverBackend breakage on HEAD. Syntactically clean, cannot commit onto broken base. Next owner: whoever resolves the FfiProverBackend adapter.",
   "Matrix CI realism: only 17 of 113 provers currently exposed via REST. Today's matrix runs a uniform wiremock suite per slug (work-convergent) — upgrade path is either (a) expand echidna REST handlers to cover all 113, or (b) specialise per-job wiremock per slug. Tracked as Package 4 step 7.",
-  "Session C's Package 4 step 6 (FfiProverBackend adapter fix) not attempted — Session C asked and was told to fix in isolated commit, but stalled on the pre-existing HEAD breakage rather than the adapter itself.",
+  "cargo check --all-targets reveals pre-existing type_info field gap in 4 test binaries (neural_property_tests, aspect_tests, e2e_prover_test, security_aspect_tests): echidna::core::{Hypothesis,Definition,Variable} gained a type_info field but test fixtures were not updated. Independent of Package 4. Needs a separate fix pass.",
 ]