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_gui_2_result.py

@@ -730,7 +730,7 @@ def test_phase_4_l3398_render_persona_editor_save_result_success():
  app._editing_persona_preferred_models_list = []
  mock_persona = MagicMock(name="mock_persona")
  mock_persona.name = "test_persona"
- with patch.object(gui_2.models, "Persona", return_value=mock_persona):
+ with patch("src.gui_2.Persona", return_value=mock_persona):
   result = gui_2._render_persona_editor_save_result(app)
  assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
  assert result.data is True
@@ -756,7 +756,7 @@ def test_phase_4_l3398_render_persona_editor_save_result_failure():
  app._editing_persona_context_preset_id = ""
  app._editing_persona_aggregation_strategy = ""
  app._editing_persona_preferred_models_list = []
- with patch.object(gui_2.models, "Persona", side_effect=RuntimeError("validation failed")):
+ with patch("src.gui_2.Persona", side_effect=RuntimeError("validation failed")):
   result = gui_2._render_persona_editor_save_result(app)
  assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
  assert result.errors, "Expected at least one error on failure"
@@ -1095,7 +1095,7 @@ def test_phase_5_l1428_request_patch_from_tier4_result_success():
  patch_text = "--- a/foo.py\n+++ b/foo.py\n@@ -1 +1 @@\n-old\n+new\n"
  mock_diff_files = [MagicMock(old_path="/proj/foo/foo.py", new_path="/proj/foo/foo.py")]
  with patch.object(gui_2.ai_client, "run_tier4_patch_generation", return_value=patch_text), \
-   patch("src.diff_viewer.parse_diff", return_value=mock_diff_files):
+   patch("src.gui_2.parse_diff", return_value=mock_diff_files):
   result = gui_2.request_patch_from_tier4_result(app, "boom", "/proj/foo/foo.py")
  assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
  assert result.data is True
@@ -1141,7 +1141,7 @@ def test_phase_5_l3163_render_tool_preset_bias_save_result_success():
  app._editing_tool_preset_scope                      = "project"
  mock_profile = MagicMock()
  mock_profile.name = "test_bias"
- with patch.object(gui_2.models, "BiasProfile", return_value=mock_profile):
+ with patch("src.gui_2.BiasProfile", return_value=mock_profile):
   result = gui_2._render_tool_preset_bias_save_result(app)
  assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
  assert result.data is True
@@ -1163,7 +1163,7 @@ def test_phase_5_l3163_render_tool_preset_bias_save_result_failure():
  app._editing_bias_profile_tool_weights              = {"foo": 2}
  app._editing_bias_profile_category_multipliers       = {"bar": 1.5}
  app._editing_tool_preset_scope                      = "project"
- with patch.object(gui_2.models, "BiasProfile", side_effect=RuntimeError("bias validation failed")):
+ with patch("src.gui_2.BiasProfile", side_effect=RuntimeError("bias validation failed")):
   result = gui_2._render_tool_preset_bias_save_result(app)
  assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
  assert result.errors, "Expected at least one error on failure"