fix: skip intermediate 'starting' notifications, only notify on failed/successful attempts

- lifecycle_hooks.publish_lifecycle_event now skips notification creation
  when event_type='instance.started' and status='starting'
- Users only see notifications for terminal states:
  - Failed: instance.error
  - Successful: instance.health_changed with status='running'
- Updated integration tests to verify new behavior:
  - test_lifecycle_started_intermediate_skips_notification
  - test_lifecycle_running_creates_notification

Quality gates: pytest 42 passed, ruff clean

apps/api/tests/integration/test_notifications_lifecycle.py

@@ -88,12 +88,12 @@ async def test_instance(db_session: AsyncSession) -> ToolInstance:
 
 @pytest.mark.asyncio
 @pytest.mark.integration
-async def test_lifecycle_event_creates_notification(
+async def test_lifecycle_started_intermediate_skips_notification(
     db_session: AsyncSession,
     event_bus: InstanceEventBus,
     test_instance: ToolInstance,
 ) -> None:
-    """Triggering a lifecycle event creates a notification for the instance owner."""
+    """Intermediate 'starting' state does NOT create a notification."""
     received: list[InstanceEventPayload] = []
 
     def subscriber(payload: InstanceEventPayload) -> None:
@@ -109,13 +109,39 @@ async def test_lifecycle_event_creates_notification(
         instance=test_instance,
         event_type="instance.started",
         status="starting",
-        message="Container started",
+        message="Container starting...",
     )
 
     # Event still published
     assert len(received) == 1
 
-    # Notification created
+    # No notification created for intermediate state
+    result = await db_session.execute(
+        select(Notification).where(Notification.user_id == test_instance.owner_id)
+    )
+    notifications = list(result.scalars().all())
+    assert len(notifications) == 0
+
+
+@pytest.mark.asyncio
+@pytest.mark.integration
+async def test_lifecycle_running_creates_notification(
+    db_session: AsyncSession,
+    event_bus: InstanceEventBus,
+    test_instance: ToolInstance,
+) -> None:
+    """Successful terminal state (running) creates a notification."""
+    from src.services.lifecycle_hooks import publish_lifecycle_event
+
+    await publish_lifecycle_event(
+        event_bus=event_bus,
+        session=db_session,
+        instance=test_instance,
+        event_type="instance.health_changed",
+        status="running",
+        message="Container running",
+    )
+
     result = await db_session.execute(
         select(Notification).where(Notification.user_id == test_instance.owner_id)
     )
@@ -124,10 +150,9 @@ async def test_lifecycle_event_creates_notification(
     n = notifications[0]
     assert n.category == "instance"
     assert n.severity == "info"
-    assert n.title == "Container started"
+    assert n.title == "Health Changed"
     assert n.source_type == "tool_instances"
     assert n.source_id == test_instance.id
-    assert n.message == "Container started"
 
 
 @pytest.mark.asyncio