fix: durably invalidate revoked session caches

[Joncallim]

Summary

Makes PostgreSQL session revocation durably schedule Redis cache invalidation without allowing Redis to authorize a session.

• records pending, claimed, deferred, and completed cache-purge state with the revocation transaction;
• deletes the digest-derived v2 key and only the applicable v1 legacy key after commit;
• retries failed deletion through the existing bounded worker maintenance sweep using FOR UPDATE SKIP LOCKED, expiring claims, and bounded backoff;
• preserves PostgreSQL revocation and expiry as the sole authority.

Evidence

• npm test — 1,580 passed, 16 environment-gated skips
• focused session/static tests — 68 passed
• npm run lint -- --max-warnings=0
• npx tsc --noEmit
• npm run build
• git diff --check

The mandatory S4 PostgreSQL command is CI-only locally: it correctly failed closed because this worktree has none of the six provisioned role URLs. The added S4 PostgreSQL state-machine proof is not conditionally skipped when CI supplies those URLs.

Scope

This child changes only session authority/cache invalidation, its existing worker maintenance hook, migration/schema parity, and focused tests. It does not alter executor, packet, history, leakage, docs, or PR #198 metadata.