Remove query-string cache-busting from static assets

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.

webui/static/hoover/router.js

@@ -5,8 +5,8 @@
  * navigation).  Link component for client-side navigation.
  */
 
-import { reactive } from './reactivity.js?v=9';
-import { h } from './vdom.js?v=9';
+import { reactive } from './reactivity.js';
+import { h } from './vdom.js';
 
 /**
  * Hash-based router.