chore(ci): standardise every workflow on Node 24 via .nvmrc

[georgeglarson]

• A human has tested these changes.

HUMAN: Ran the full check set against this branch on Node 24.20 in a clean container: lint reports 0 errors, build succeeds, Prettier is clean, and all 309 tests pass across 18 suites. The workflow changes themselves are only exercisable by this PR's own CI run.

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Why

From #proj-agent-canvas, 2026-08-29:

Well 22 is old too, we would like to support 24+

We need to simplify all these workflows where we can, so we can do more without being dragged down by, for example, TWO CI runs, one for 22 and another for 24

So I'd like to kill Node 22, and make all stuff run well on Node 24

Six workflow files each hardcoded their own Node literal, eleven pins in total, so every bump meant eleven synchronised edits. The test job ran the whole suite twice, once on 22.12 and once on 24.x.

The 22.12 floor was already fiction. 63 packages in package-lock.json declare engines.node above it: the eslint set wants ^20.19.0 || ^22.13.0 || >=24, @hey-api/* wants >=22.18.0. Nothing fails today only because npm warns rather than errors without engine-strict.

Summary

• Every setup-node step now reads a single .nvmrc containing 24, so the next bump is one file instead of eleven.
• The test job's [22.12, 24.x] matrix is removed rather than reduced to one element, so CI runs once.
• CONTRIBUTING.md moves its stated floor to Node 24 to match.

No runtime code changes and no package.json change, so nothing here affects what consumers install.

Issue Number

No issue filed. Requested in Slack, quoted above.

How to Test

npm ci && npm run lint && npm run build && npm run format:check && npm test

Green on Node 24.20.0: 18 suites, 309 tests, 0 lint errors.

The rest is CI config, so this PR's own checks are the real test. The test job should appear once rather than twice, and every job should resolve its Node from .nvmrc.

Video/Screenshots

Type

• Bug fix
• Feature
• Refactor
• Breaking change
• Docs / chore

Notes

npm-publish.yml keeps its explicit npm install -g npm@latest. Node 24.0.0 shipped npm 11.3.0, under the 11.5.1 that trusted publishing needs, and .nvmrc floats across the 24.x line, so that step is still load-bearing. Its comment claimed "Node 22 bundles npm 10.x" and now gives the real reason.

Two follow-ups, kept out deliberately so this one stays a pure chore:

• An engines: { "node": ">=24" } floor. That narrows the published support range, which is semver-major, and this repo squash-merges, so bundling it here would make the whole PR breaking and force a 2.0 on merge. It belongs in its own PR where that call can be made on its own merits. Branch is ready if you want it: georgeglarson:feat-node-24-engines.
• Removing the ws dependency. With the floor at 24 that fallback branch is dead code, and deleting it subsumes fix(events): use global WebSocket in Node ESM #362's edit. Happy to open that next.

[all-hands-bot]

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