P1 bug reported by greptile-apps: MultiEdit uses toolInput.edits[].file_path,
not toolInput.file_path. The gate was silently allowing all MultiEdit calls.
Fix: separate MultiEdit into its own branch that iterates edits array
and gates on the first unchecked file_path.
9/9 tests pass.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>