docs(store): describe PostgreSQL consistency and integration checks

Author: nosam1998

crates/adapters/gfa-store/README.md

@@ -1,4 +1,4 @@
-# SQLite match persistence
+# Match persistence
 
 `SqliteMatchStore` implements the storage port in `gfa-service`. Inject an
 `Arc<SqliteMatchStore>` into the lifecycle service when wiring a host.
@@ -31,5 +31,26 @@ python3 .github/scripts/sqlite-query-check.py verify
 ```
 
 When a query is removed, also remove its obsolete `.sqlx/query-*.json` file.
-This adapter stores the initial match event model; searchable metadata,
-retention policies, snapshots, and PostgreSQL support are separate increments.
+## PostgreSQL
+
+Enable the `postgres` feature and connect with
+`PostgresMatchStore::connect(url).await`. The pool applies the embedded
+`migrations/postgres` migrations at startup. Use a dedicated database and include
+`sslmode=verify-full` for a remote database. Call `close().await` on shutdown.
+
+PostgreSQL appends lock the match row before checking receipts and revisions.
+Snapshot reads use a repeatable-read transaction; assist counters use atomic
+upserts. Match IDs have C collation so cursor ordering agrees with the service.
+The SQLite and PostgreSQL adapters implement the same storage port.
+
+The PostgreSQL CI job compiles queries against a fresh migration-derived schema,
+checks the committed PostgreSQL metadata, and runs the ignored integration test
+against a separate empty database. To run it locally, set `DATABASE_URL` to a
+migrated query-checking database and `GFA_TEST_POSTGRES_URL` to an isolated empty
+test database, then run:
+
+```sh
+cargo test -p gfa-store --no-default-features --features postgres --locked -- --ignored
+```
+
+Retention policies and materialized replay snapshots are separate increments.