feat(gui): Rename gui.py to gui_legacy.py and update references

tests/conftest.py

@@ -24,7 +24,7 @@ def kill_process_tree(pid):
     except Exception as e:
         print(f"[Fixture] Error killing process tree {pid}: {e}")
 
-@pytest.fixture(scope="session", params=["gui.py", "gui_2.py"])
+@pytest.fixture(scope="session", params=["gui_legacy.py", "gui_2.py"])
 def live_gui(request):
     """
     Session-scoped fixture that starts a GUI script with --enable-test-hooks.

tests/test_gui2_performance.py

@@ -67,11 +67,11 @@ def test_performance_parity():
     """
     Compare the metrics collected in the parameterized test_performance_benchmarking.
     """
-    if "gui.py" not in _shared_metrics or "gui_2.py" not in _shared_metrics:
+    if "gui_legacy.py" not in _shared_metrics or "gui_2.py" not in _shared_metrics:
         if len(_shared_metrics) < 2:
             pytest.skip("Metrics for both GUIs not yet collected.")
 
-    gui_m = _shared_metrics["gui.py"]
+    gui_m = _shared_metrics["gui_legacy.py"]
     gui2_m = _shared_metrics["gui_2.py"]
     
     # FPS Parity Check (+/- 15% leeway for now, target is 5%)