4613f895ab
The stale-write guard now refuses write_file on an existing file the task never read in full, so test_write_file_rewrite_hint's overwrite-without-read fixtures were refused before the hint could be computed. Reading first is the exact read->whole-file-rewrite pattern the hint exists for. tools-reference.md's write_file row now mirrors the WRITE_FILE_SCHEMA description (one-sentence contract + the recovery step) instead of a longer paraphrase.