## Why
Tool response delivery handles kept discarded results alive until the cell ended.
## What changed
Add a local V8 handle scope in `resolve_tool_response` so delivery handles are released when response delivery finishes. Live promises continue to retain their results.
## Testing
Add a regression test that verifies a live promise preserves its response through garbage collection and that dropping the promise makes the response collectible before the cell ends.
GitOrigin-RevId: a74e78acae3ec9a465694d7503150aee123792ec
