Genotoxic skill: what it does and how to install it

What it does. Builds a Trailmark code graph and pre-analysis, runs a language-appropriate mutation framework and optionally Necessist, then maps survived mutants and unnecessary test statements to production functions. Writes GENOTOXIC_REPORT.md with corroborated findings, false positives, missing tests and fuzzing targets, using complexity, reachability and blast-radius data.

When to use it. Use it after mutation testing on a codebase with an existing passing test suite to prioritise test improvements and fuzzing work. Do not use it for codebases without tests, documentation or configuration changes, or trivial single-file scripts.