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.

src/rag_engine.py

@@ -8,10 +8,11 @@ from dataclasses import dataclass, field, fields as dc_fields
 from typing import List, Dict, Any, Optional
 
 from src import ai_client
-from src import models
 from src import mcp_client
-from src.result_types import ErrorInfo, ErrorKind, NilRAGState, Result
-from src.type_aliases import Metadata
+from src import models
+from src.mcp_client          import RAGConfig
+from src.result_types       import ErrorInfo, ErrorKind, NilRAGState, Result
+from src.type_aliases       import Metadata
 
 from src.file_cache import ASTParser
 
@@ -121,7 +122,7 @@ def _parse_search_response_result(res_str: str) -> Result[List[Dict[str, Any]]]:
 
 
 class RAGEngine:
- def __init__(self, config: models.RAGConfig, base_dir: str = "."):
+ def __init__(self, config: RAGConfig, base_dir: str = "."):
   self.config             = copy.deepcopy(config)
   self.base_dir           = base_dir
   self.client             = None