dashboard: browser notifications for operator-bound events

three signals fire OS notifications:
- new approval lands in the queue (per id, via /api/state delta)
- new ask_operator question queued (per id)
- broker message sent to operator (live via SSE)

first /api/state render after page load seeds the 'seen' sets
without firing — only items that arrive while the page is open
count. controls in a row under the banner: 🔔 enable
notifications (calls requestPermission, hides on grant), 🔕 mute /
🔔 unmute toggle (localStorage-backed so operator can silence
without revoking the permission), inline status text when blocked
or unsupported.

notification tag='hyperhive' collapses rapid bursts; onclick
focuses the dashboard tab. requires secure context (HTTPS or
localhost) — on other origins the API is unavailable and the
controls hide themselves.

todo: entry dropped.

TODO.md

@@ -44,29 +44,6 @@ Pick anything from here when relevant. Cross-cutting design notes live in
 
 ## UI / UX
 
-- **Browser notifications for operator-bound events.** Dashboard
-  pings the OS notification center when (a) a new approval lands
-  in the queue, (b) a new `ask_operator` question is queued, (c) a
-  broker message is sent `to: "operator"`. All three data sources
-  are already in `/api/state` + `/messages/stream` so this is
-  pure frontend. Sketch:
-  1. Small "🔔 enable notifications" button somewhere (header
-     or near the inbox section). Clicks call
-     `Notification.requestPermission()`. Hide once granted.
-  2. Track last-seen counts in the JS app
-     (`approvals.length`, `questions.length`). On
-     `refreshState`, if the count went up, fire
-     `new Notification(...)` per new item.
-  3. SSE handler for `messages/stream` fires a notification on
-     `kind === 'sent' && to === 'operator'` (already triggers
-     `refreshState`; just adds a notify call alongside).
-  4. Notification body links back to the dashboard (`onclick →
-     window.focus()` + section anchor).
-  Caveats: Notification API requires a secure context (HTTPS or
-  localhost). Most operators access via LAN / Tailscale — works
-  fine for localhost forwards, otherwise needs a TLS cert in the
-  module. Persist a per-browser "muted" toggle in localStorage so
-  the operator can silence without revoking permission.
 
 - **Terminal: `/model` slash command.** Operator-typeable model
   override from the terminal. Depends on the model-override work