fix(phase3): Resolve remaining test failures and stabilize GUI

- Fixed
ullcontext NameError in gui_2.py.
- Corrected TestMMAApprovalIndicators to call real rendering methods on mock app.
- Updated 	est_history_manager.py to provide required context_files argument to UISnapshot.
- Stabilized 	est_z_negative_flows.py with robust polling for terminal response status and corrected field names.
- Cleaned up debug logging in 
ag_engine.py and pp_controller.py.

tests/test_history_manager.py

@@ -70,6 +70,7 @@ class TestHistoryManager:
             auto_add_history=True,
             disc_entries=[{"role": "user", "content": "hello"}],
             files=[{"path": "a.txt"}],
+            context_files=[],
             screenshots=["screenshot.png"],
         )
         d = snap.to_dict()
@@ -85,6 +86,7 @@ class TestHistoryManager:
         assert restored.auto_add_history == snap.auto_add_history
         assert restored.disc_entries == snap.disc_entries
         assert restored.files == snap.files
+        assert restored.context_files == snap.context_files
         assert restored.screenshots == snap.screenshots
 
     def test_push_clears_redo_stack(self):