fix(routing): remove unused imports to pass CI lint

Remove unused `pathlib.Path` and `RegistryNotFoundError` from resolver.py
and unused `tempfile` from test_routing_core.py, resolving ruff F401 errors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/aipass/routing/resolver.py

@@ -4,10 +4,9 @@ Branch resolution logic.
 Resolves symbolic @branch names to absolute paths and metadata.
 """
 
-from pathlib import Path
 from typing import Any, Dict, List, Optional
 
-from .exceptions import BranchNotFoundError, RegistryNotFoundError
+from .exceptions import BranchNotFoundError
 from .registry import get_all_branches, get_branch_by_name, load_registry
 
 

tests/test_routing_core.py

@@ -5,7 +5,6 @@ Tests all Phase 1 routing functions with >80% coverage target.
 """
 
 import json
-import tempfile
 from pathlib import Path
 
 import pytest