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_rag_engine_ready_status_bug.py

@@ -37,10 +37,10 @@ def test_rag_engine_init_with_local_provider_raises_when_sentence_transformers_m
  when sentence-transformers is not installed.
  """
  from src import models
- config = models.RAGConfig(
+ config = RAGConfig(
    enabled=True,
    embedding_provider="local",
-   vector_store=models.VectorStoreConfig(provider="chroma", collection_name="test"),
+   vector_store=VectorStoreConfig(provider="chroma", collection_name="test"),
  )
  # Force the import to fail
  with patch.dict(sys.modules, {"sentence_transformers": None}):
@@ -125,10 +125,10 @@ def test_rag_engine_init_with_failing_local_embedding_leaves_engine_broken() ->
  """
  from src import models
  from src import rag_engine
- config = models.RAGConfig(
+ config = RAGConfig(
    enabled=True,
    embedding_provider="local",
-   vector_store=models.VectorStoreConfig(provider="chroma", collection_name="t"),
+   vector_store=VectorStoreConfig(provider="chroma", collection_name="t"),
  )
  with patch("src.rag_engine._get_sentence_transformers",
     side_effect=ImportError("Local RAG embeddings require sentence-transformers.")):