U1/U2/KTD-6: extract the dashboard heap-runner's process-group kill lifecycle
into a shared scripts/lib/run-vitest-watchdog.mjs with per-class budget bands
(timings only tighten within a generous ceiling) and an inline hang-diagnostics
snapshot. Delegate run-vitest-with-heap.mjs to it (behavior preserved). Add
timeout-minutes backstops to all full-suite.yml test jobs so a wedged run can no
longer hang to GitHub's 6h ceiling.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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