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_mcp_config.py

@@ -9,7 +9,7 @@ def test_mcp_server_config_to_from_dict():
         "args": ["server.js"],
         "auto_start": True
     }
-    cfg = models.MCPServerConfig.from_dict("test-server", data)
+    cfg = MCPServerConfig.from_dict("test-server", data)
     assert cfg.name == "test-server"
     assert cfg.command == "node"
     assert cfg.args == ["server.js"]
@@ -31,7 +31,7 @@ def test_mcp_configuration_to_from_dict():
             }
         }
     }
-    cfg = models.MCPConfiguration.from_dict(data)
+    cfg = MCPConfiguration.from_dict(data)
     assert len(cfg.mcpServers) == 2
     assert cfg.mcpServers["server1"].command == "python"
     assert cfg.mcpServers["server2"].url == "http://localhost:8080/sse"
@@ -47,7 +47,7 @@ def test_load_mcp_config(tmp_path):
     config_file.write_text(json.dumps(data))
     
     # We'll need a way to load from a specific path
-    # Maybe models.load_mcp_config(path)
-    cfg = models.load_mcp_config(str(config_file))
+    # Maybe load_mcp_config(path)
+    cfg = load_mcp_config(str(config_file))
     assert "test" in cfg.mcpServers
     assert cfg.mcpServers["test"].command == "echo"