PR #2054 — Cross-Harness Review Provenance Survives a Missing Cost Row

The goalpost we inherited

The previous reliability work made synlynk pr check enforce cross-harness and cross-model review using measured dispatch provenance. That gate should remain fail-closed: a reviewer must not be allowed to merge when the implementing identity is unknown.

The problem this PR addresses

A successful dispatch can still lose its cost_entries row when job status tracking records a false negative. In that case, the gate had no way to connect a real implementation PR back to its daemon job, even though dispatch branch names already carry the job identity.

What shipped

• synlynk/db.py now falls back, after the existing capability-rating and linked-story lookups, to a PR head branch shaped like dispatch/<harness>/job-<id>.
• The fallback requires a matching daemon_jobs row and uses its harness and resolved/requested model. Existing cost-ledger evidence remains preferred.
• synlynk cost log accepts the concise --story spelling and --job-id, so interactive sessions can record the missing link.
• A missing-provenance check emits a one-line stderr reminder while preserving the hard failure.

Verification

The focused suite passes: tests/test_agent_cli.py reports 147 passed and 1 skipped; the cost/database regression set reports 161 passed. New tests cover branch-based recovery, fail-closed behavior without a daemon row, and the existing cost-entry path.

New goalpost

Review provenance is now resilient to a missing cost ledger row without turning an unresolvable PR into an approved one. The next reliability step is to keep job status and cost capture aligned at the source so the fallback remains a rare recovery path.