Align CI and validation on release check

[rogerchappel]

Summary

• include npm pack --dry-run in the local validation script
• make CI run the package release:check entrypoint instead of a hand-maintained command list
• document release:check as the contributor verification command

Verification

• npm run release:check
• npm run validate

Notes

npm ci was required in the fresh worktree before validation; npm reported existing audit findings during install but the release checks passed.