GitHub Actions is deprecating the Node.js 20 runtime, with enforcement
starting June 2, 2026. This updates the action to use node24 runtime.
- action.yml: change `using: "node20"` to `using: "node24"`
- package.json: bump `@types/node` from ^20.16.5 to ^24
Fixes#122
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
