fix: resolve CI lint and mypy errors

- test_chain_concurrency.py: fix isort ordering (_MAX_CHAIN_RETRIES
  before _is_integrity_error, merge third-party/first-party groups)
- storage_pg.py: add type: ignore for untyped DDL call (SQLAlchemy stubs)

Author: bradleygauthier

reference/python/src/qp_capsule/storage_pg.py

@@ -71,7 +71,7 @@ class CapsuleModelPG(PGBase):
 event.listen(
     CapsuleModelPG.__table__,
     "after_create",
-    DDL(
+    DDL(  # type: ignore[no-untyped-call]
         "CREATE UNIQUE INDEX IF NOT EXISTS uq_capsule_global_sequence "
         "ON quantumpipes_capsules (sequence) WHERE tenant_id IS NULL"
     ).execute_if(dialect="postgresql"),

reference/python/tests/test_chain_concurrency.py

@@ -21,9 +21,8 @@
 from unittest.mock import AsyncMock
 
 import pytest
-
 from qp_capsule.capsule import Capsule, TriggerSection
-from qp_capsule.chain import CapsuleChain, _is_integrity_error, _MAX_CHAIN_RETRIES
+from qp_capsule.chain import CapsuleChain, _MAX_CHAIN_RETRIES, _is_integrity_error
 from qp_capsule.exceptions import CapsuleError, ChainConflictError, ChainError, StorageError