fix(imports): complete migration from 'from src import models' to direct subsystem imports

Replaces the broken-script-generated imports in src/ and tests/ with
clean direct imports from the destination modules. Per user directive:
'we should adjust the tests instead' — no legacy __getattr__ shim is
re-introduced.

Key fixes:
- src/mcp_client.py: remove self-import (MCPServerConfig etc. are defined
  locally; the script's module-top self-import caused the circular
  ImportError blocking all 11 test tiers)
- src/gui_2.py: add missing module-top imports for FileItem, ContextFileEntry,
  ContextPreset, Tool, Persona, BiasProfile, parse_history_entries;
  remove broken-script local imports inside function bodies
- src/app_controller.py: remove FileItem/FileItems from the type_aliases
  import block (was shadowing the direct import with the forward-reference
  TypeAlias string, breaking isinstance() calls); confirm isinstance()
  now works
- src/commands.py: script correctly removed unused 'from src import models'
- tests/test_models_no_top_level_tomli_w.py: import save_config_to_disk
  from src.project (no legacy shim back in models.py)
- tests/test_rag_engine_ready_status_bug.py: import RAGConfig and
  VectorStoreConfig from src.mcp_client
- tests/test_gui_2_result.py: patch src.gui_2.Persona/BiasProfile
  (gui_2 binds at module load; src.personas patch doesn't affect the
  gui_2 namespace)
- tests/test_gui_2_result.py: patch src.gui_2.parse_diff (it lives in
  gui_2, not patch_modal)
- tests/test_generate_type_registry.py: Metadata is now a dataclass in
  src_type_aliases.md (not a TypeAlias in type_aliases.md); src_models.md
  is no longer generated (src/models.py has no dataclasses after the
  de-cruft track)

No local imports inside function bodies (per python.md §17.9a). All
new imports are at module top with surgical edits.

tests/test_models_no_top_level_tomli_w.py

@@ -41,12 +41,13 @@ def test_models_does_not_import_tomli_w_at_module_level() -> None:
 def test_models_can_still_call_save_config_after_lazy_load() -> None:
  """save_config() must work even though tomli_w is lazy-loaded."""
  import src.models
+ from src.project import save_config_to_disk
  config = {
   "ai": {"provider": "minimax", "model": "MiniMax-M3", "temperature": 0.0},
   "theme": {"palette": "solarized_dark", "font_size": 16.0},
  }
  try:
-  src.models.save_config_to_disk(config)
+  save_config_to_disk(config)
  except Exception as e:
   pytest.fail(f"save_config raised after lazy tomli_w: {e}")
  finally:
@@ -57,13 +58,14 @@ def test_models_can_still_call_save_config_after_lazy_load() -> None:
 def test_save_config_uses_tomli_w_on_demand() -> None:
  """First call to save_config() should trigger tomli_w import (subsequent calls hit sys.modules cache)."""
  import src.models
+ from src.project import save_config_to_disk
  # Drop tomli_w from sys.modules if it was already loaded (e.g. by other tests)
  if "tomli_w" in sys.modules:
   del sys.modules["tomli_w"]
  assert "tomli_w" not in sys.modules
  # Call save_config - this should trigger the import
  try:
-  src.models.save_config_to_disk({"test_key": "test_value"})
+  save_config_to_disk({"test_key": "test_value"})
  except Exception:
   # We don't care if the save itself fails; we just want to verify
   # the import happened.