Drop ?v=N version pins from all JS imports and HTML <link>/<script> tags.
Cache invalidation is now handled solely by server-side cache-control headers.
Update docs and AGENTS.md accordingly.
- update-vendor.sh now creates webui/vendor symlinks (htm.js)
- install.sh calls update-vendor.sh after package install
- Add vendor/.empty and webui/vendor/.empty as directory placeholders in git