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/test_persistence_enums.py

@@ -0,0 +1,45 @@
+"""Lock the persistence enum string values + members.
+
+These enums are mirrored by Postgres enum types, embedded in stored DB
+rows, and surfaced in the JSON API. Renaming a value (or removing a
+member) silently breaks production data and previously-issued API
+responses, so the strings + the set of members are the contract.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from app.automations.persistence.enums.automation_status import AutomationStatus
+from app.automations.persistence.enums.run_status import RunStatus
+from app.automations.persistence.enums.trigger_type import TriggerType
+
+pytestmark = pytest.mark.unit
+
+
+def test_automation_status_string_values_are_stable() -> None:
+    """The exact strings persisted to Postgres and served in API JSON."""
+    assert {member.value for member in AutomationStatus} == {
+        "active",
+        "paused",
+        "archived",
+    }
+
+
+def test_run_status_string_values_are_stable() -> None:
+    """Run lifecycle states embedded in the ``automation_runs`` table."""
+    assert {member.value for member in RunStatus} == {
+        "pending",
+        "running",
+        "succeeded",
+        "failed",
+        "cancelled",
+        "timed_out",
+    }
+
+
+def test_trigger_type_keeps_manual_member_even_though_unregistered() -> None:
+    """``MANUAL`` is reserved (mirrors the Postgres enum) but the trigger
+    store does not register it in v1. The enum must keep both members so
+    existing DB rows and the schema migration plan stay valid."""
+    assert {member.value for member in TriggerType} == {"schedule", "manual"}