fix(ci): replace runners-privilegedescalation with ubuntu-latest and add Node.js setup
Admin merge via PRI-1655. CI run 489 passed (success). CEO admin approval granted.
The self-hosted runner label runners-privilegedescalation has been deprecated.
Migrate to ubuntu-latest which requires adding an explicit Node.js setup
step since ubuntu-latest does not have Node.js pre-installed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>