fix(tests): the rule-history fixture must not delete a book the embedder is still writing (#3241)

The integration lane failed on a deadlock, not an assertion — 103 passed, and
the one error was in teardown: `DELETE FROM rulebooks` blocked against
another process holding a lock on a rule row.

`update_rule` fires a detached asyncio.create_task(upsert_rule_embedding(...))
that opens its OWN connection and UPDATEs the rule it just saved. The
teardown's rulebook delete cascade-locks that same row, and Postgres resolves
the cycle by killing one of them. The sibling test_integration_rule_verification
never hit this because it calls update_rule but never deletes its rulebook.

Cleanup moves to setup, which runs on a fresh loop after the previous test's
loop has closed and cancelled whatever it left in flight. That also keeps the
#3240 constraint intact: no database call after a yield.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_integration_rule_versions.py

@@ -35,10 +35,13 @@ OWNER_USERNAME = "rule_history_owner"
 async def constraint():
     """One rule carrying a check, with no history yet.
 
-    Cleanup is in this fixture's own teardown, never in an autouse one:
+    CLEANED UP AT SETUP, NOT TEARDOWN, and that is forced. `update_rule` fires
-    `_dispose_engine` arrives through usefixtures, so it tears down BEFORE an
+    a detached `asyncio.create_task(upsert_rule_embedding(...))` that opens
-    autouse fixture would, and a database call after that point orphans a
+    its own connection and UPDATEs the rule row. A teardown that deleted the
-    pooled connection and breaks the NEXT test to touch Postgres (#3240).
+    rulebook would race it: the delete cascade-locks the rule the embedding
+    task is writing, and Postgres kills one of them with a deadlock. Purging
+    at setup instead runs on a fresh loop, after the previous test's loop
+    closed and cancelled whatever it left in flight.
     """
     async with async_session() as s:
         owner = await ensure_user(s, OWNER_USERNAME)
@@ -60,13 +63,7 @@ async def constraint():
         verify_with="read the workflow's shell setting",
     )
 
-    yield {"uid": uid, "rule_id": rule.id}
+    return {"uid": uid, "rule_id": rule.id}
-
-    async with async_session() as s:
-        row = await s.get(Rulebook, book.id)
-        if row is not None:
-            await s.delete(row)
-        await s.commit()
 
 
 async def _versions(rule_id: int) -> list[RuleVersion]: