docs: add proof pack v0.2 roadmap

Author: Proof Pack Bot

docs/proof-pack/ROADMAP_v0.2.md

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+# Roadmap v0.2 — Proof Pack adversarial inspection targets
+
+This document records the inspection result for Proof Pack v0.1 and the
+candidate next proof-surface targets for v0.2. It is a custody artefact,
+not a marketing document.
+
+## 1. Current v0.1 boundary
+
+Proof Pack v0.1 is bounded to:
+
+- a path-local Python harness driving the existing CommitGate kernel
+- a synthetic signature verifier (accepts records where
+  `signature == "sig_valid"`)
+- an in-memory nonce ledger
+- a fixed clock pinned to `2026-04-27T05:01:00Z`
+- a single mutation callback
+- reproducible JSON fixtures and content-addressed receipts
+
+## 2. What v0.1 proves
+
+On the demonstrated path, with the harness above:
+
+- a DENY decision prevents the `mutation_callback` from executing
+- receipts record both ALLOW and DENY outcomes
+- each DENY receipt emits a `no_execution_marker`
+- the four fixture cases and their receipts are byte-for-byte replayable
+
+## 3. What v0.1 does not prove
+
+v0.1 does not prove:
+
+- real cryptographic signature verification (the verifier is synthetic)
+- persistent nonce custody across process restarts
+- cross-process replay resistance
+- concurrent safety under simultaneous `execute()` calls
+- distributed side-effect control beyond the in-process callback
+- production readiness
+
+## 4. v0.2 candidate targets
+
+The following are candidate proof surfaces, each scoped to remain
+inspectable without expanding the public claim:
+
+- Ed25519 or ECDSA signature verification against a fixed public key,
+  with a malformed-signature fixture
+- a persistent nonce ledger (file- or sqlite-backed) with a restart-
+  replay fixture
+- a cross-process replay test that consumes a nonce in one process and
+  asserts refusal in a second
+- a concurrent `execute()` test under a shared nonce ledger, asserting
+  that at most one mutation occurs per nonce
+- malformed-JSON and parser-boundary fixtures (truncated input, wrong
+  types, extra fields) with matching DENY receipts
+
+## 5. Claim boundary
+
+- This roadmap does not claim production infrastructure, certification,
+  adoption, or universal runtime governance.
+- It records the next bounded proof surfaces for authority-before-
+  mutation inspection.
+- v0.2 targets remain candidate work until implemented, tested, and
+  reviewed.