v2

Reusable node-pr-ci recipe. Same interface as v1 (workflow_call inputs node-version/runs-on; runs npm ci && npm run ci:pr).

Change vs v1: actions/checkout and actions/setup-node bumped @v4 -> @v6 so the action wrapper runs on the Node 24 runtime (GitHub forces this from 2026-06-16). The node-version input default (20.19.0) is unchanged — this does not change the tested Node runtime.

Migrate consumers from @v1 to @v2 deliberately.