feat(api): add PATCH /api/graph/project/<id> to update project name

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/graph.py

@@ -91,6 +91,23 @@ def delete_project(project_id: str):
     })
 
 
+@graph_bp.route('/project/<project_id>', methods=['PATCH'])
+def patch_project(project_id: str):
+    """Update mutable project fields (currently: name)."""
+    project = ProjectManager.get_project(project_id)
+    if not project:
+        return jsonify({"success": False, "error": t('api.projectNotFound', id=project_id)}), 404
+
+    body = request.get_json(silent=True) or {}
+    name = body.get("name", "").strip()
+    if not name:
+        return jsonify({"success": False, "error": "name cannot be empty"}), 400
+
+    ProjectManager.save_project({"id": project_id, "name": name})
+    updated = ProjectManager.get_project(project_id)
+    return jsonify({"success": True, "data": updated})
+
+
 @graph_bp.route('/project/<project_id>/reset', methods=['POST'])
 def reset_project(project_id: str):
     """

backend/tests/test_project_patch.py

@@ -0,0 +1,37 @@
+import pytest
+from unittest.mock import patch, MagicMock
+from app import create_app
+
+
+@pytest.fixture
+def app():
+    return create_app({'TESTING': True})
+
+
+@pytest.fixture
+def client(app):
+    return app.test_client()
+
+
+def test_patch_project_name_success(client):
+    mock_project = {"id": "proj_123", "project_id": "proj_123", "name": "Old Name"}
+    updated = {**mock_project, "name": "New Name"}
+    with patch('app.api.graph.ProjectManager.get_project', side_effect=[mock_project, updated]), \
+         patch('app.api.graph.ProjectManager.save_project'):
+        resp = client.patch('/api/graph/project/proj_123', json={"name": "New Name"})
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert data["success"] is True
+
+
+def test_patch_project_name_not_found(client):
+    with patch('app.api.graph.ProjectManager.get_project', return_value=None):
+        resp = client.patch('/api/graph/project/nonexistent', json={"name": "X"})
+    assert resp.status_code == 404
+
+
+def test_patch_project_name_empty_rejected(client):
+    mock_project = {"id": "proj_123", "project_id": "proj_123", "name": "Old"}
+    with patch('app.api.graph.ProjectManager.get_project', return_value=mock_project):
+        resp = client.patch('/api/graph/project/proj_123', json={"name": "   "})
+    assert resp.status_code == 400