fix(gui): Resolve ImGui stack corruption, JSON serialization errors, and test regressions

tests/test_file_item_model.py

@@ -7,6 +7,7 @@ def test_file_item_fields():
  assert item.path == "src/models.py"
  assert item.auto_aggregate is True
  assert item.force_full is False
+ assert item.injected_at is None
 
 def test_file_item_to_dict():
  """Test that FileItem can be serialized to a dict."""
@@ -14,7 +15,8 @@ def test_file_item_to_dict():
  expected = {
   "path": "test.py",
   "auto_aggregate": False,
-  "force_full": True
+  "force_full": True,
+  "injected_at": None
  }
  assert item.to_dict() == expected
 
@@ -23,12 +25,14 @@ def test_file_item_from_dict():
  data = {
   "path": "test.py",
   "auto_aggregate": False,
-  "force_full": True
+  "force_full": True,
+  "injected_at": 123.456
  }
  item = FileItem.from_dict(data)
  assert item.path == "test.py"
  assert item.auto_aggregate is False
  assert item.force_full is True
+ assert item.injected_at == 123.456
 
 def test_file_item_from_dict_defaults():
  """Test that FileItem.from_dict handles missing fields."""
@@ -37,3 +41,4 @@ def test_file_item_from_dict_defaults():
  assert item.path == "test.py"
  assert item.auto_aggregate is True
  assert item.force_full is False
+ assert item.injected_at is None