Add state management, WebSocket polling, html.js templating, and refactor pages

- lib/state.py: per-subsystem collectors with versioned state store
- daemon/server.py: state refresh on request, batch routing updates
- webui/static/hoover/html.js: new html tag template helper via htm.js
- webui/static/hoover/websocket.js: real-time state change notifications
- webui/static/hoover/vdom.js: VDOM improvements for keyed diff
- All frontend pages refactored to use html templates
- Add tests for state management and polling
- Update docs and AGENTS.md

webui/static/pages/notfound.js

@@ -1,4 +1,4 @@
-import { h, PageHeader, definePage } from '/static/hoover/index.js?v=7';
+import { html, PageHeader, definePage } from '/static/hoover/index.js?v=7';
 
 export default definePage({
     init() {
@@ -7,9 +7,9 @@ export default definePage({
     render(state) {
         return [
             PageHeader({ title: '404' }),
-            h('div', { class: 'card' },
-                h('div', { class: 'card-body text-muted' }, 'Page not found: ' + state.path),
-            ),
+            html`<div class="card">
+                <div class="card-body text-muted">Page not found: ${state.path}</div>
+            </div>`,
         ];
     },
 });