Real-toolchain probes for tools/mutation-table.sh (Soul's 2026-10-01 scratch repo, committed).
Run each on Yggdrasil through the stopgap; expected rows:
 rust/mutants-a.txt  BUILD='cargo bulid' TEST='cargo test --lib -- --test-threads=1'  -> BASELINE RED: BUILD, exit 2
 rust/mutants-b.txt  (same TEST, no BUILD)  -> forge row SURVIVED, caught=0, exit 1
 rust/mutants-c.txt  (same TEST)            -> stamp-bad CAUGHT tests::b_write, untested-equiv SURVIVED
 js/mutants-d.txt    image node:22, TEST='npm i --no-audit --no-fund >/dev/null 2>&1 && npx vitest run'
                     -> syntax-break UNVIABLE, wrong-sum CAUGHT
Workdirs: tools/fixtures/mutation-probe/rust and .../js.
 soul2/mutants.txt   TEST='cargo test --lib -- --test-threads=1', workdir .../soul2 -> a test keeps state in an IGNORED file
                     (target/soul-cache.txt): stamp2-bad CAUGHT tests::d_cache, untested-equiv SURVIVED, add-minus CAUGHT
                     tests::c_add; exit 1. Before the per-mutant snapshot, untested-equiv read CAUGHT d_cache and the job
                     exited 0 (the cache outlived the mutant that wrote it).
 fresh/mutants.txt   TEST='cargo test --lib -- --test-threads=1', workdir .../fresh (f_fresh creates a directory, so it cannot
                     run twice) -> `SNAPSHOT RED (exit 101) for: cargo test ...`, "no rows counted", exit 2. Before the control
                     run of the unmutated snapshot, the job read untested-equiv CAUGHT tests::f_fresh and exited 0.
 jsr/mutants.txt     workdir .../jsr, each mutant carries its own `test:` (jest 29.7.0 and vitest 3.2.4 from npm), image node:22 ->
                     jest-load UNVIABLE, jest-wrong CAUGHT add › adds, jest-exit ERROR (process.exit(1) names no test),
                     jest-equiv SURVIVED, vt-load UNVIABLE, vt-wrong CAUGHT, vt-equiv-throw-at-load UNVIABLE; exit 1.
                     (Before the fixes jest-load read ERROR and jest-exit read CAUGHT | process.exit called with "1".)
RUN_ON_HOST watchdog probe (tools/stopgap/ygg-verify.sh): RUN_ON_HOST=1 TIMEOUT=60 ygg-verify.sh <repo> HEAD rust
 'echo cwd=$PWD; sleep 300; echo hostdone' -> cwd is the job's work directory, `TIMEOUT after 60s`, exit 124, no `hostdone`,
 no sleep left on the host. With trap "exit 0" TERM around the sleep the status is still 124 (it was 0).
