[bokelley]

Part of #1695. This adds the PostgreSQL conformance test for the stores merged in #1724, as a test: commit so it releases nothing.

tests/conformance/reporting/test_reporting_subscriptions_pg.py covers PgReportingSubscriptionStateStore and PgPrincipalRecordStore on a real database, each test in its own schema:

• idempotent schema creation;
• compare-and-swap semantics: insert-if-absent, a stale revision refused, revision increments;
• 20 concurrent writers losing nothing;
• a restarted seller: a new PrincipalService and ReportingSubscriptionEngine on the same database serve the same get_principal readback and owe identical periods and coverage.

The module skips without ADCP_PG_TEST_URL. CI's core Postgres lane already runs tests/conformance/reporting/ with it set, so no workflow change is needed. Locally against PostgreSQL 16: 4 passed.

Refs #1695

🤖 Generated with Claude Code

[aao-secretariat]

Ladon verdict: Approve

Approve.

Test-only PR: one new 147-line Postgres conformance test for PgReportingSubscriptionStateStore and PgPrincipalRecordStore, shipped under a test: commit, releasing nothing. No no-auto-approve team match, gated_paths false, high_risk false, first review.

Reviewer verified imports resolve, CAS assertions match the store's INSERT-ON-CONFLICT/UPDATE-WHERE-revision semantics, the 20-writer concurrency test is a correct optimistic-retry loop, and asyncio_mode=auto covers undecorated async tests/fixtures. No blocking or medium findings.

One low follow-up (non-blocking, omitted from gate): the pool fixture reimplements isolated_reporting_pool but drops its finally-based teardown, leaking the random-named test schema on failure — worth tidying but not merge-blocking.

Decision table: rows 1–8 do not fire (no critical/high/medium findings, no gate, no team match). Falls through to row 9 → approve.