fix: add type hints in cleanup_unused_files.py

Updates type annotations to use built-in types like `list` and `dict`, and uses `| None` for optional types, along with adding `from __future__ import annotations`

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 832522395

Author: GWeale

contributing/samples/adk_agent_builder_assistant/tools/cleanup_unused_files.py

@@ -14,10 +14,9 @@
 
 """Cleanup unused files tool for Agent Builder Assistant."""
 
+from __future__ import annotations
+
 from typing import Any
-from typing import Dict
-from typing import List
-from typing import Optional
 
 from google.adk.tools.tool_context import ToolContext
 
@@ -26,11 +25,11 @@
 
 
 async def cleanup_unused_files(
-    used_files: List[str],
+    used_files: list[str],
     tool_context: ToolContext,
-    file_patterns: Optional[List[str]] = None,
-    exclude_patterns: Optional[List[str]] = None,
-) -> Dict[str, Any]:
+    file_patterns: list[str] | None = None,
+    exclude_patterns: list[str] | None = None,
+) -> dict[str, Any]:
   """Identify and optionally delete unused files in project directories.
 
   This tool helps clean up unused tool files when agent configurations change.