release(v4.7.0): peer-presence events for instant BroadcastChannel revoke

Adds the bridge-connection-lifecycle signal that closes Prism's
~45s revoke window down to one server→client round-trip (~50ms).

Server (`@shade/inbox-server`):
- `inbox.peer_connected` / `inbox.peer_disconnected` events on the
  0↔1 boundary across WS + SSE bridges. Long-poll deliberately not
  tracked (every poll boundary would flap; push transports are also
  the only ones where instant revoke matters).
- `PresenceTracker` collapses two parallel bridges (e.g. WS + SSE
  during fallback handover) into one connect/disconnect pair.
- `GET /v1/bridge/presence` SSE endpoint: signed query with
  `kind: 'presence'`, `watched: string[]`; on open streams a
  per-address snapshot, then change frames filtered server-side.
  MAX_WATCHED_ADDRESSES = 64. Subscribing does not itself count as
  a peer-bridge connection.
- `createBridgeRoutes` now returns `{ app, websocket, presence }`.

Client (`@shade/transport-bridge`):
- `PresenceBridge.subscribe({ watch, onPresenceChange })` →
  `{ addPeer, removePeer, watching, unsubscribe }`. addPeer/removePeer
  mutate via reconnect with a fresh signed query.
- `signPresenceQuery` helper for non-PresenceBridge consumers.

Tests cover all four acceptance criteria from the Prism request:
server-event smoke, online→offline subscription, address scoping
(carol invisible to a [alice]-only sub), reconnect, plus an
addPeer/removePeer regression.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-inbox-server/src/events.ts

@@ -21,6 +21,19 @@ export interface InboxServerEventMap {
   'inbox.expired_purged': { count: number };
   'inbox.rate_limited': { route: string; key: string };
   'inbox.quota_rejected': { address: string; reason: 'address-quota' | 'sender-quota' | 'body-too-large' };
+  // V4.7 — bridge presence transitions. Emitted on the 0↔1 boundary
+  // across tracked transports for a given address. Long-poll is
+  // intentionally NOT tracked: an LP client toggles in/out of a request
+  // every few seconds, and the resulting flapping would dominate the
+  // event stream. Push transports (WS, SSE) are also the only ones
+  // where the ~50ms revoke window for `BroadcastChannel.removeMember`
+  // matters — long-poll users are already on a slow path.
+  'inbox.peer_connected': { address: string; bridgeKind: 'ws' | 'sse' };
+  'inbox.peer_disconnected': {
+    address: string;
+    bridgeKind: 'ws' | 'sse';
+    reason: 'closed' | 'error';
+  };
 }
 
 export type InboxServerEventName = keyof InboxServerEventMap;