Replaces polling merge-bot with event-driven CI. When all checks pass, the workflow squash-merges automatically.
HTML validation, JS syntax check, JSON validation, file size budget. Auto-merge handled by nexus-merge-bot.sh until Gitea runner is set up.
Co-authored-by: Claude (Opus 4.6) <claude@hermes.local> Co-committed-by: Claude (Opus 4.6) <claude@hermes.local>