chore: deps and CI improvements (#4660)

* chore: deps

- Replace .tool-versions and .nvmrc with .mise.toml
- Update CONTRIBUTING.md to reference mise

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: use lts/* for codeQuality CI job

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: test on Node 18, 20, 22, and 24

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: test on Node 18, 20, and 22

Node versions match Ubuntu LTS defaults:
- 18 = Ubuntu 24.04
- 20 = Ubuntu 25.x
- 22 = Ubuntu 26.04

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: remove nvm and asdf references, use mise only

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: pin vitest to ~4.0.18 to maintain Node 18 support

Using tilde (~) pins to 4.0.x, avoiding 4.1.x which introduced
rolldown and dropped Node 18 support.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>