## Problem
A Node test job wedged on a macOS runner: the **Run Node tests** step (`node --test`) hung for **over an hour** while the identical tests passed in ~1.5 min on every other runner (Node 20 macOS same run: 1m46s; Node 18 macOS on a sibling PR: 1m34s). It is a one-off stuck process — the macOS analogue of the documented `setup-node` Windows CDN flake — not a real Node 18 vs 20 difference.
No job in `ci.yml` set any `timeout-minutes`, so a hung step runs toward GitHub's **6h default** before the platform kills it.
## Changes
- **Job-level `timeout-minutes: 20` backstop on all 15 jobs.** The slowest real job is ~5 min, so 20 min is generous headroom (survives cold-cache spikes) while turning a 6h hang into a 20-min fail. The clock counts execution time only — queued/waiting time does not count against it.
- **`Run Node tests` wrapped in `nick-fields/retry` (SHA-pinned, v4.0.0):** a hung attempt is killed after 6 min and retried once (`timeout_minutes: 6`, `max_attempts: 2`), so a one-off wedge self-heals without a manual re-run. Normal run is well under a minute; worst case 2×6 min stays under the 20-min job backstop.
## Notes
- New SHA-pinned third-party action (`nick-fields/retry@ad98453…` = v4.0.0) — satisfies the SHA-pin convention; `zizmor` runs on this PR.
- `ci.yml` validated as well-formed YAML; all 15 jobs confirmed to carry a job-level timeout.
kingchenc
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