feat: v0.5.0 header, switcher, phone key bar, shared polling, Matrix "needs you"

- Header: no SSO chip ("Sign in again" only on expiry), state dot on the
  session chip, LIVE as a dot, ⋯ menu for text size/notifications/fullscreen,
  Panels badge for waiting sessions and alerts.
- Session switcher on the chip; bare URL reattaches the last session; + New
  opens the panel form with project folders.
- Notifications when other sessions start waiting; alerts polled with the
  panels closed; one tab polls for all tabs over BroadcastChannel.
- Sidebar: context bar per session instead of the Context panel; compact
  Repo/CI with "Ask Claude to fix CI"; legible labels.
- Phone: key bar, drawer with backdrop, visualViewport-aware layout, DOM
  renderer on touch, compact connection dot.
- devdesk-notify-matrix: one Matrix message per wait that lasts
  DEVDESK_MATRIX_DELAY seconds with nobody attached.

Closes #8
Closes #13
Closes #14
Closes #15
Closes #16
Closes #17
Closes #28

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/notify.js

@@ -32,11 +32,29 @@ export async function requestNotifications() {
   return Notification.requestPermission();
 }
 
+const MUTE_KEY = 'devdesk.notify.muted';
+
+export function isMuted() {
+  try {
+    return localStorage.getItem(MUTE_KEY) === '1';
+  } catch {
+    return false;
+  }
+}
+
+export function setMuted(muted) {
+  try {
+    localStorage.setItem(MUTE_KEY, muted ? '1' : '0');
+  } catch {
+    // Private mode: the mute just won't persist.
+  }
+}
+
 export function ring(session, detail) {
   if (attentive()) return;
   unread += 1;
   render();
-  if (notificationsState() === 'granted') {
+  if (notificationsState() === 'granted' && !isMuted()) {
     const note = new Notification(`Claude · ${session || 'devdesk'}`, {
       body: detail || 'Claude needs your attention',
       tag: `devdesk-${session}`,