feat(automation): register agent_task action and schedule/manual triggers

surfsense_backend/app/automations/registries/actions/__init__.py

@@ -12,3 +12,6 @@ __all__ = [
     "get_action",
     "register_action",
 ]
+
+# Built-in actions self-register at import time.
+from . import agent_task  # noqa: E402, F401

surfsense_backend/app/automations/registries/actions/agent_task.py

@@ -0,0 +1,27 @@
+"""Built-in ``agent_task`` action. Self-registers at import time."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from app.automations.schemas.actions import AgentTaskActionParams
+
+from .store import register_action
+from .types import ActionDefinition
+
+
+async def _handle_agent_task(args: dict[str, Any]) -> dict[str, Any]:
+    """Stub. Validates params; real wiring lands with the executor."""
+    AgentTaskActionParams.model_validate(args)
+    return {"status": "stubbed"}
+
+
+AGENT_TASK_ACTION = ActionDefinition(
+    type="agent_task",
+    name="Agent task",
+    description="Run an agent task with a scoped tool allowlist.",
+    params_schema=AgentTaskActionParams.model_json_schema(),
+    handler=_handle_agent_task,
+)
+
+register_action(AGENT_TASK_ACTION)