test(automations): cross-cutting registries, enums, side-effects + shared fixtures

Top-level tests that span multiple submodules:

- test_stores.py (7): the trigger + action registry contracts — register
  round-trip, unknown type → None (not raise), duplicate registration
  rejected, defensive snapshot from all_*.
- test_definition_types.py (2): params_schema property on both
  ActionDefinition and TriggerDefinition reflects the Pydantic model.
- test_persistence_enums.py (3): exact string values + member sets of
  AutomationStatus / RunStatus / TriggerType — the postgres-mirrored
  contract that breaks stored rows if drifted.
- test_import_registrations.py (2): the bundled agent_task action and
  schedule trigger self-register on package import (canary for the
  side-effect import chain).

conftest.py adds isolated_action_registry / isolated_trigger_registry
fixtures: snapshot + restore of the module-level _REGISTRY dicts so
tests that add their own definitions don't leak across the suite.

14 tests, pure unit.

surfsense_backend/tests/unit/automations/conftest.py

@@ -0,0 +1,39 @@
+"""Shared fixtures for the ``app.automations`` unit-test tree.
+
+Provides registry isolation: the built-in ``schedule`` trigger and
+``agent_task`` action self-register at import time. Tests that register
+additional triggers/actions (or assert on the registry contents) must
+not leak that state to other tests. These fixtures snapshot and restore
+the module-level registry dicts.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterator
+
+import pytest
+
+from app.automations.actions import store as action_store
+from app.automations.triggers import store as trigger_store
+
+
+@pytest.fixture
+def isolated_action_registry() -> Iterator[None]:
+    """Snapshot and restore the action registry around a test."""
+    snapshot = dict(action_store._REGISTRY)
+    try:
+        yield
+    finally:
+        action_store._REGISTRY.clear()
+        action_store._REGISTRY.update(snapshot)
+
+
+@pytest.fixture
+def isolated_trigger_registry() -> Iterator[None]:
+    """Snapshot and restore the trigger registry around a test."""
+    snapshot = dict(trigger_store._REGISTRY)
+    try:
+        yield
+    finally:
+        trigger_store._REGISTRY.clear()
+        trigger_store._REGISTRY.update(snapshot)