Add check_matched_pair_drift() at module level in store.py — read-only
audit of the Claim.matched_remittance_id ↔ Remittance.claim_id FK pair.
Logs WARNING on drift with up to 5 examples of each of two cases
(claim-side and remit-side), returns the count of drifted rows. Wired
into api.py::lifespan right after db.init_db() and ensure_clearhouse_seeded(),
wrapped in try/except so a query failure logs but doesn't crash boot.
The symmetric-write + symmetric-clear invariants on
manual_match / manual_unmatch were already correct; this commit pins
them with focused regression tests in test_store_match_invariant.py
(8 tests covering both directions, both happy-path, rollback pin, and
drift-check unit behavior). PCN asymmetry in the fixture prevents the
auto-match inside CycloneStore.add (Task 10) from pre-pairing, so
manual_match is the only writer.
Migration 0016 adds the missing ix_claims_matched_remittance_id index —
the drift check scans WHERE matched_remittance_id IS NOT NULL on every
boot and would become a full-table scan past ~10k claims. Symmetric
with ix_remittances_claim_id (added in 0007). Migration tests bumped
from head=15 to head=16.
Nora
f5d119fbe7