fix: never allow the projects directory to become a project directory

Loading a .gns3 placed directly in the projects root registered the
shared projects directory as the project path (load_project derives
the path from the file's parent directory). Deleting such an entry ran
rmtree on the projects directory itself, wiping every project until a
root-owned file stopped it, and left a zombie entry in the controller.

Three layers of protection:

- Controller.load_project() refuses a .gns3 whose parent directory is
  the projects directory; the normal subdirectory layout is unaffected
- the Project.path setter rejects the projects directory itself and
  its ancestors, closing the same hole for POST/PUT with an explicit
  path
- Project.delete() uses realpath + commonpath instead of commonprefix:
  entries whose path is the projects root are refused, and sibling
  directories sharing a string prefix (/srv/projects-evil vs
  /srv/projects) are no longer treated as inside the projects dir

Also removes the project_load MCP tool: loading by raw server
filesystem path is a footgun for automated clients; projects can still
be opened by project_id via the remaining tools.

tests/controller/test_controller.py

@@ -125,6 +125,54 @@ async def test_load_projects_skip_unexpected_errors(controller, projects_dir):
     mock_load_project.assert_called_with(os.path.join(projects_dir, "broken_project", "broken.gns3"), load=False)
 
 
+def _write_topology_file(path, project_id, name):
+    with open(path, "w+") as f:
+        json.dump(
+            {
+                "name": name,
+                "project_id": project_id,
+                "version": __version__,
+                "revision": 10,
+                "type": "topology",
+                "topology": {"computes": [], "drawings": [], "links": [], "nodes": []},
+            },
+            f,
+        )
+
+
+@pytest.mark.asyncio
+async def test_load_project_refuses_gns3_in_projects_directory(controller, projects_dir):
+    """
+    A .gns3 placed directly in the projects directory must not be
+    loadable: its parent directory (the shared projects root) would become
+    the project directory, and deleting that project would wipe every
+    project on the controller.
+    """
+
+    topology_file = os.path.join(projects_dir, "root-level.gns3")
+    _write_topology_file(topology_file, str(uuid.uuid4()), "root-level")
+
+    with pytest.raises(ControllerError):
+        await controller.load_project(topology_file)
+    assert not controller._projects
+
+
+@pytest.mark.asyncio
+async def test_load_project_from_own_subdirectory(controller, projects_dir):
+    """
+    The normal layout — a .gns3 inside its own subdirectory — keeps
+    loading, with the subdirectory as the project directory.
+    """
+
+    project_dir = os.path.join(projects_dir, "sub-project")
+    os.makedirs(project_dir)
+    topology_file = os.path.join(project_dir, "sub-project.gns3")
+    _write_topology_file(topology_file, str(uuid.uuid4()), "sub-project")
+
+    project = await controller.load_project(topology_file, load=False)
+    assert project.path == project_dir
+
+
 def test_projects_directory_event_handler_filters_events(controller):
 
     controller._notify_projects_directory_event = MagicMock()

tests/controller/test_import_project.py

@@ -87,7 +87,8 @@ async def test_import_project_override(projects_dir, controller):
     override the previous keeping the same project id & location
     """
 
-    tmpdir = Path(projects_dir)
+    tmpdir = Path(projects_dir) / "override-location"
+    tmpdir.mkdir(parents=True, exist_ok=True)
     project_id = str(uuid.uuid4())
     topology = {
         "project_id": project_id,

tests/controller/test_project.py

@@ -741,6 +741,37 @@ async def test_delete(project):
     assert not os.path.exists(project.path)
 
 
+@pytest.mark.asyncio
+async def test_delete_refuses_to_delete_projects_directory(project, projects_dir):
+    """
+    A poisoned entry whose path is the projects directory itself (a .gns3
+    loaded directly from the projects root before the guard existed) must
+    not be deletable: rmtree would wipe every project on the controller.
+    """
+
+    other_project = os.path.join(projects_dir, "another-project")
+    os.makedirs(other_project, exist_ok=True)
+
+    # Simulate the poisoned in-memory state directly: the path setter now
+    # rejects such an assignment, but a long-running server can still hold
+    # an entry created before the fix.
+    project._path = projects_dir
+
+    with pytest.raises(ControllerError):
+        await project.delete()
+    assert os.path.exists(other_project)
+
+
+def test_path_setter_rejects_projects_directory(project, projects_dir):
+    """
+    The projects directory itself must never become a project directory.
+    """
+
+    with pytest.raises(ControllerForbiddenError):
+        project.path = projects_dir
+    assert project.path == os.path.join(projects_dir, project.id)
+
+
 @pytest.mark.asyncio
 async def test_delete_does_not_start_nodes(project):
     """

tests/controller/test_project_open.py

@@ -192,12 +192,14 @@ async def test_open(controller, projects_dir):
         "version": "2.0.0"
     }
 
-    with open(os.path.join(projects_dir, "demo.gns3"), "w+") as f:
+    project_dir = os.path.join(projects_dir, "demo")
+    os.makedirs(project_dir)
+    with open(os.path.join(project_dir, "demo.gns3"), "w+") as f:
         json.dump(simple_topology, f)
 
     project = Project(name="demo",
                       project_id="64ba8408-afbf-4b66-9cdd-1fd854427478",
-                      path=str(projects_dir),
+                      path=project_dir,
                       controller=controller,
                       filename="demo.gns3",
                       status="closed")