fix(verify): stop re-compaction poison from fail-closing the verification gate

[alpertarhan]

Fixes #72

Root cause (confirmed in code)

Three poison classes fed the verification gate stale/self-referential "constraints":

1. Own error prose — the operator pastes a VerificationGateError back into the session; the next run mines "do not bypass verification" as a prohibition. Retrying adds evidence the next retry is checked against.
2. [x] completion records — the prior summary's Done items are records, not rules.
3. Superseded rules — "Do not push/open PR yet…" released later by the user; the factually correct new summary contradicts the stale rule → semantic-contradiction = −20, gaps.length > 0 → 80/100 → permanent fail-closed (inconsistency gaps are not deterministically patchable).

Fix — three layers

Layer	Change
Extraction	isNonLiveConstraintText filters own gate/notify prose, [x] items, and compaction status lines from constraint mining + state sanitization
Retirement	retireSupersededConstraints marks a constraint superseded when a later user message releases it. Deferral rules ("do not push yet") accept a terse release ("ok push it now") via anchor polarity flip; standing rules ("never commit directly to main") keep the strict rich-contradiction check — a terse imperative sharing one verb cannot silently drop a live rule. The replacement is kept as critical context
Wiring	Extract step computes overrides once (rc.factOverrides); post-synthesis and post-state gates consume them via VerificationEvidence.factOverrides; buildState persists them so applyContinuityOverrides drops the stale rule from the merged state and the continuity capsule cannot re-poison the next generation

Verified

• Exact issue signature reproduced in a test: poisoned extraction + faithful new-state summary → inconsistency gap, ok: false. With retirement → 100/100, zero gaps.
• 19 new regression tests (poison classes, retirement semantics, gate, persistence).
• Full suite: 1008 pass / 0 fail; bun run typecheck (4 tsconfigs) and bun run build clean.

Notes for the reporter

• The fail-closed posture is unchanged — only the extraction/gate inputs got smarter.
• Stale compact-extraction-<session>.json caches replay old constraints, but the gate-side isNonLiveConstraintText + retirement filters apply to cache-derived constraints too, so an in-place upgrade self-heals without clearing caches.