etna-ify

Turn one fix commit into a full mutation+property+witness workload atom, verify it, and commit it

Build src/bin/etna.rs as a programmatic, framework-agnostic dispatcher over (tool, property) pairs

End-to-end sanity check — etna workload check passes, base builds, every variant is detected, every framework drives its crate

Scan the entire git history of a Rust project and identify every bug-fix commit as a mutation candidate

Regenerate BUGS.md and TASKS.md via `etna workload doc` — docs are derived, never hand-edited