[sai5880]

Summary

Fixes #7655. delete_files had confirm_deletion: bool = True in its tool signature, so the model controlled the approval flag and the tool never used the framework human-in-the-loop confirmation gate. The flag has been removed and the tool now requires confirmation through the framework.

Changes

• Removed the confirm_deletion parameter and the early-return block from src/google/adk/cli/built_in_agents/tools/delete_files.py.
• Updated the docstring so it states that confirmation is collected by the framework, not supplied as an argument.
• Registered the tool as FunctionTool(delete_files, require_confirmation=True) in src/google/adk/cli/built_in_agents/adk_agent_builder_assistant.py.
• Removed the stale confirm_deletion=True argument from tests/unittests/cli/test_resolve_root_directory.py.
• Added tests/unittests/cli/test_delete_files.py, which verifies that the registered tool requires confirmation, that a model-supplied confirm_deletion argument cannot bypass the gate, and that an approved call still deletes the file.
• Checked the other tools on the same assistant. cleanup_unused_files only scans and does not delete, and no other write/delete tool used this flag.

Tests

uv run pytest tests/unittests/cli/test_delete_files.py tests/unittests/cli/test_resolve_root_directory.py tests/unittests/cli/test_adk_agent_builder_assistant.py -q

Result: 19 passed.

Fixes #7655