test(procrastinate): scope app fixture per-test

session-scope broke when run_worker's open_async() tore down the sync
sub-connector PsycopgConnector creates lazily for sync defer(). The
outer `with app.open():` didn't reopen it for the next test, so test 2's
defer hit AppNotOpen. Function-scoped + idempotent apply_schema is the
simplest reliable shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: snopoke

integration_tests/test_procrastinate.py

@@ -36,14 +36,17 @@ def _check_log_errors(caplog):
             pytest.fail(f"log errors during '{when}': {errors}")
 
 
-@pytest.fixture(scope="session")
+@pytest.fixture
 def app():
     # Async connector even though the tests are sync: run_worker raises
     # SyncConnectorConfigurationError on SyncPsycopgConnector. Async works in both contexts.
+    #
+    # Function-scoped because run_worker tears down the sync sub-connector
+    # PsycopgConnector creates inside `app.open()`, and nothing reopens it for
+    # the next test's defer() call. Cheap: apply_schema is idempotent.
     conn = procrastinate.PsycopgConnector(conninfo=PROCRASTINATE_DSN)
     app = procrastinate.App(connector=conn)
     with app.open():
-        # Apply schema (idempotent — Procrastinate's apply_schema is safe to re-run).
         app.schema_manager.apply_schema()
         yield app