fix(pwa): wire up manifest link + SW registration so install prompt works

The PWA was configured end-to-end in vite.config.ts and built the
manifest + service worker correctly, but neither was ever loaded by
the browser — no <link rel="manifest"> in the HTML and no script
registering the generated registerSW.js. Chrome therefore never fired
beforeinstallprompt, no install icon appeared in the URL bar, and the
hand-rolled PwaUpdatePrompt hung on navigator.serviceWorker.ready
because no SW had been registered.

Changes:
- Render pwaInfo.webManifest.linkTag into <svelte:head> in the root
  layout so Chrome finds the hashed manifest.
- Replace the hand-rolled SW-update logic in PwaUpdatePrompt with
  useRegisterSW() from virtual:pwa-register/svelte — it registers the
  worker (immediate: true) and exposes reactive needRefresh +
  updateServiceWorker stores that match registerType: 'prompt'.
- Add triple-slash refs to vite-plugin-pwa/info and /svelte in
  app.d.ts for the virtual module types.
- Set manifest.id = startUrl in @mana/shared-pwa so Chrome doesn't
  warn and keeps the install identity stable across start_url edits.
- Keep devEnabled: false and expand the comment: the 2026-04-08
  dreams mic-button bug and the /offline navigateFallback both
  misbehave when Workbox precache doesn't run under vite dev. Test
  the install flow via `pnpm build && pnpm preview` instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared-pwa/src/config.ts

@@ -62,6 +62,10 @@ export function createPWAConfig(options: PWAConfigOptions): PWAConfig {
 
 	// Build manifest
 	const manifest: ManifestConfig = {
+		// Pin the app identity to the start URL. Without `id`, Chrome derives
+		// one from start_url and warns in DevTools; it also refuses to
+		// re-prompt an install if start_url ever changes.
+		id: startUrl,
 		name,
 		short_name: shortName,
 		description,

packages/shared-pwa/src/types.ts

@@ -139,6 +139,13 @@ export interface ManifestIcon {
  * Full manifest configuration
  */
 export interface ManifestConfig {
+	/**
+	 * Unique manifest identifier. Chrome uses this to correlate the installed
+	 * app with its manifest across `start_url` changes. Strongly recommended
+	 * by the spec since 2023 — omitting it triggers a DevTools warning and
+	 * can suppress the install prompt on re-installs.
+	 */
+	id: string;
 	name: string;
 	short_name: string;
 	description: string;