Memex 0.4: evidence quality milestone

[giulioleone097]

What changed

• Adds MemexBench-Code v1: 4 fixtures, 224 frozen queries/qrels, deterministic lexical/vector/graph/hybrid ablations, immutable fingerprints, no-vector proof, and fail-closed category/signal gates.
• Adds portable ev1:<sha256> evidence identity, provenance lineage, and identity-based top-k deduplication.
• Adds truthful read-only retrieval_health CLI/MCP operation with separate source/cache/registry/host/live proof layers, real index/vendor/freshness probes, recovery signals, and dashboard projection.
• Backports the minimum Memex 0.3.3 prerequisite contracts required by the actual remote main baseline and aligns superseded 0.2 regression expectations.

Why

Implements Linear milestone 0.4 — Evidence Quality (MX-04-01/02/03).

Verification

• CI verify: pass — build, typecheck, lint, full test suite
• CI run: https://github.com/giulioleone097/memex/actions/runs/29726091833
• Head: 070401cf22be957e9261f08ab769d9bebda17503
• Focused runtime/packaging/storage regression: 30/30 pass
• MemexBench gate: pass; 224 queries, minimum Recall@5 0.91518, deterministic no-vector, zero category/signal failures
• Exact-diff review: CLEAN; no P0-P2 open

State

Draft PR intentionally retained for review. The previous remote-baseline blocker is resolved; GitHub reports mergeStateStatus: CLEAN and CI is green.

[giulioleone097]

CI blocker confirmed against remote main: missing unpublished 0.3.3 prerequisite exports (GRAPH_ACTIONS/GraphAction), version module, and phase-aware wiki check contract. Canonical local 0.3.3 branch remains green: lint/typecheck/build, 72 focused tests, MemexBench gate, independent CLEAN review. Keep draft until baseline 0.3.3 is published/rebased.

[giulioleone097]

Remote-baseline blocker resolved in 2de6c8c + 070401c. Clean-clone CI run 29726091833 is green: build, typecheck, lint, and full test suite all pass. Head 070401cf22be957e9261f08ab769d9bebda17503; GitHub merge state is CLEAN. Draft retained for review, not because of an open technical blocker.