feat: expose embed command_id in note API responses (#545)

* feat: expose embed command_id in note API responses

Note.save() already returns the command_id from the embed_note
background job, but the API routes discarded it. This surfaces
the command_id in NoteResponse for both POST and PUT endpoints,
enabling callers to poll GET /api/commands/jobs/{command_id} to
know when embedding has completed.

* Add tests for note API command_id response

tests/test_notes_api.py

@@ -0,0 +1,115 @@
+from unittest.mock import AsyncMock, patch
+
+import pytest
+from fastapi.testclient import TestClient
+
+
+@pytest.fixture
+def client():
+    """Create test client after environment variables have been cleared by conftest."""
+    from api.main import app
+
+    return TestClient(app)
+
+
+class TestNoteCreation:
+    """Test suite for Note API endpoints."""
+
+    @patch("api.routers.notes.Note")
+    def test_create_note_returns_command_id(self, mock_note_cls, client):
+        """Test that creating a note returns the embed command_id."""
+        mock_note = AsyncMock()
+        mock_note.id = "note:abc123"
+        mock_note.title = "Test Note"
+        mock_note.content = "Some content"
+        mock_note.note_type = "human"
+        mock_note.created = "2026-01-01T00:00:00Z"
+        mock_note.updated = "2026-01-01T00:00:00Z"
+        mock_note.save.return_value = "command:embed123"
+        mock_note.add_to_notebook = AsyncMock()
+        mock_note_cls.return_value = mock_note
+
+        response = client.post(
+            "/api/notes",
+            json={"content": "Some content", "note_type": "human"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["command_id"] == "command:embed123"
+        assert data["id"] == "note:abc123"
+
+    @patch("api.routers.notes.Note")
+    def test_create_note_command_id_none_when_no_content_embedding(
+        self, mock_note_cls, client
+    ):
+        """Test that command_id is None when save returns None (no embedding)."""
+        mock_note = AsyncMock()
+        mock_note.id = "note:abc456"
+        mock_note.title = "Empty Note"
+        mock_note.content = "Some content"
+        mock_note.note_type = "human"
+        mock_note.created = "2026-01-01T00:00:00Z"
+        mock_note.updated = "2026-01-01T00:00:00Z"
+        mock_note.save.return_value = None
+        mock_note.add_to_notebook = AsyncMock()
+        mock_note_cls.return_value = mock_note
+
+        response = client.post(
+            "/api/notes",
+            json={"content": "Some content", "note_type": "human"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["command_id"] is None
+
+
+class TestNoteUpdate:
+    """Test suite for Note update endpoint."""
+
+    @patch("api.routers.notes.Note")
+    def test_update_note_returns_command_id(self, mock_note_cls, client):
+        """Test that updating a note returns the embed command_id."""
+        mock_note = AsyncMock()
+        mock_note.id = "note:abc123"
+        mock_note.title = "Test Note"
+        mock_note.content = "Original content"
+        mock_note.note_type = "human"
+        mock_note.created = "2026-01-01T00:00:00Z"
+        mock_note.updated = "2026-01-01T00:00:00Z"
+        mock_note.save.return_value = "command:embed789"
+        mock_note_cls.get = AsyncMock(return_value=mock_note)
+
+        response = client.put(
+            "/api/notes/note:abc123",
+            json={"content": "Updated content"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["command_id"] == "command:embed789"
+
+    @patch("api.routers.notes.Note")
+    def test_update_note_command_id_none_when_no_embedding(
+        self, mock_note_cls, client
+    ):
+        """Test that command_id is None on update when no embedding is triggered."""
+        mock_note = AsyncMock()
+        mock_note.id = "note:abc123"
+        mock_note.title = "Test Note"
+        mock_note.content = "Some content"
+        mock_note.note_type = "human"
+        mock_note.created = "2026-01-01T00:00:00Z"
+        mock_note.updated = "2026-01-01T00:00:00Z"
+        mock_note.save.return_value = None
+        mock_note_cls.get = AsyncMock(return_value=mock_note)
+
+        response = client.put(
+            "/api/notes/note:abc123",
+            json={"title": "Updated Title"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert data["command_id"] is None