fix(lotus-denoise): reliability — never-silent watchdog, resume timeout, cache + activation

Track-A robustness fixes from the engine review; no quality/model changes.

- H1: auto-resume the AudioContext on `statechange` if it suspends mid-call
  (mobile backgrounding / audio interruption). Previously the dest node emitted
  digital silence with no recovery — a silent mute of the sender.
- H2: `resumeCtx()` races `resume()` against a timeout. A suspended context can
  only resume on a user gesture; the action can arrive via postMessage, so a
  bare `await resume()` inside LiveKit's track-change lock could hang and
  deadlock all later mute/unmute/device-switch. Now it proceeds and the H1
  watcher heals it.
- M1: don't cache a REJECTED wasm fetch — a transient blip during a reconnect
  used to permanently disable denoise for the session. Evict on failure.
- M2: activate denoise off `allConnections$` (local participant's connections)
  instead of `livekitRoomItems$`, which excludes the local participant and only
  surfaces rooms with a remote member — so denoise now also runs when you're
  alone and no longer couples to a remote-render concern.
- Context lifecycle: `closeContext()` removes the state watcher before closing;
  `ensureContext()` closes a half-initialised context on any failure (no leak).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lotus/lotusDenoise.ts

@@ -101,8 +101,12 @@ export function startLotusDenoise(vm: CallViewModel): () => void {
   const roomListeners = new Map<LivekitRoom, () => void>();
   let rooms: LivekitRoom[] = [];
 
-  const sub = vm.livekitRoomItems$.subscribe((items) => {
-    const next = items.map((i) => i.livekitRoom);
+  // Drive activation off the LOCAL participant's connection(s), not
+  // `livekitRoomItems$` — that stream excludes the local participant and only
+  // surfaces rooms with ≥1 remote member, so it wouldn't denoise you while
+  // you're alone and is a fragile coupling to a remote-render concern.
+  const sub = vm.allConnections$.subscribe((data) => {
+    const next = data.getConnections().map((c) => c.livekitRoom);
     rooms = next;
     for (const [room, off] of roomListeners) {
       if (!next.includes(room)) {