refactor(consumers): replace 'models.<moved_class>' with direct imports

Per post_module_taxonomy_de_cruft_20260627 Phase 2 (FR7 continued).
The previous migration commit (8f11340b) handled the
'from src.models import X' pattern (85 sites). This commit handles
the 'models.<moved_class>' attribute access pattern (44 sites in 20
files), which the __getattr__ shim previously supported.

The migration was performed by the one-time script
scripts/tier2/artifacts/post_module_taxonomy_de_cruft_20260627/migrate_models_attr.py
which:
 1. For each 'models.<moved_class>' reference, replaces it with the
    bare class name (e.g., 'models.MCPConfiguration' -> 'MCPConfiguration')
 2. Adds the import 'from src.<destination> import <moved_class>' at
    the top of the file (deduplicated if the import already exists)
 3. Skips moved classes that the file already imports directly

The migration script inserts the import after the 'from __future__
import annotations' line if present; otherwise it adds the import
to the destination module's existing import block. Two files
required manual fixes because the script's regex didn't handle them:
 - src/rag_engine.py: uses 'from src import models' (not 'from
                            src.models import X'); the class is accessed
                            via 'models.RAGConfig'. Replaced with a
                            direct 'from src.mcp_client import RAGConfig'
                            import and removed the 'from src import models'.
 - tests/test_project_context_20260627.py: uses the parens-style
                            multi-line 'from src.models import (X, Y, Z)'.
                            Replaced with the parens-style direct import.

After this commit:
 - 'models.MCPConfiguration', 'models.FileItem', 'models.Ticket', etc.
   no longer work in src/ and tests/ (the AttributeError raises
   because models.py no longer has the __getattr__ entries for
   moved classes)
 - All consumer files have direct imports of the moved classes

Total: 44 'models.<moved_class>' references rewritten across 20 files.

tests/test_gui_kill_button.py

@@ -37,7 +37,7 @@ def test_render_ticket_queue_table_columns():
   from src.gui_2 import App, render_ticket_queue
   app = App.__new__(App)
   app.active_track = MagicMock()
-  app.active_tickets = [models.Ticket(id="T-001", description="Test task", priority="medium", status="in_progress")]
+  app.active_tickets = [Ticket(id="T-001", description="Test task", priority="medium", status="in_progress")]
   app.ui_selected_tickets = set()
   app.ui_selected_ticket_id = None
   app.controller = MagicMock()