Build the GitHub Action with the repo's Node - #1380

The Build GitHub Action job now builds with the repo's Node, through the setup-node composite (Node 26, npm ci). Before, it ran npm install --include=dev on the default Node of the runner (22, with npm 10). That npm removes the "libc" entries that the committed services/action/package-lock.json has, so Check for changes found a diff.

On branches that step is continue-on-error, so the drift was hidden. On tags it is strict, so every tag run failed and the Release job was skipped.

• npm ci never writes the lockfile, so Check for changes now checks only the built dist/.
• I checked the v0.6.14 release commit: Node 22 and Node 20 reproduce the 4 "libc" removals. Node 26 with npm ci gives no diff, and the built dist/index.js does not change.