lotus(#1): ML denoise as a first-class audio TrackProcessor (fixes A7)

Implements RNNoise/Speex noise suppression as a LiveKit audio
TrackProcessor attached to the local mic track, replacing the host's
build-time getUserMedia monkeypatch. Because EC re-attaches the processor
on every (re)publish (LocalTrackPublished), denoise now survives EC's
mid-call reconnect — the root cause of A7 "mic dead after reconnect".
Reuses the worklet/wasm assets already shipped under ./denoise/ (no new EC
dependency); model/gate configured via lotusDenoise/lotusModel/lotusGate
URL params. Additive: no-op unless lotusDenoise=ml.

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

src/lotus/lotusDenoise.ts

@@ -0,0 +1,98 @@
+/*
+Copyright 2026 Lotus Guild
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import {
+  type LocalAudioTrack,
+  ParticipantEvent,
+  type Room as LivekitRoom,
+  Track,
+} from "livekit-client";
+import { logger } from "matrix-js-sdk/lib/logger";
+
+import { type CallViewModel } from "../state/CallViewModel/CallViewModel";
+import { lotusFlag, lotusParam } from "./lotusWidget";
+import {
+  type LotusDenoiseConfig,
+  LotusDenoiseProcessor,
+} from "./lotusDenoiseProcessor";
+
+/**
+ * Apply Lotus ML noise suppression to the local mic track as a first-class
+ * Element Call audio TrackProcessor (#1), replacing the host's build-time
+ * `getUserMedia` monkeypatch.
+ *
+ * Opt-in via `lotusDenoise=ml` (+ `lotusModel`, `lotusGate`,
+ * `lotusGateThreshold`, `lotusDenoiseBase`). Because the processor is attached
+ * to the mic publication and re-attached on every (re)publish, denoise
+ * survives EC's mid-call reconnect — fixing the A7 "mic dead after reconnect"
+ * bug. Additive: no-op without the flag.
+ */
+export function startLotusDenoise(vm: CallViewModel): () => void {
+  if (lotusParam("lotusDenoise") !== "ml") return () => undefined;
+
+  const config: LotusDenoiseConfig = {
+    model: lotusParam("lotusModel") === "speex" ? "speex" : "rnnoise",
+    assetBase: lotusParam("lotusDenoiseBase") || "./denoise/",
+    gate: lotusFlag("lotusGate"),
+    gateThreshold: Number(lotusParam("lotusGateThreshold")) || -50,
+  };
+
+  const micOf = (room: LivekitRoom): LocalAudioTrack | undefined =>
+    room.localParticipant.getTrackPublication(Track.Source.Microphone)
+      ?.track as LocalAudioTrack | undefined;
+
+  const apply = (room: LivekitRoom): void => {
+    const mic = micOf(room);
+    if (mic && !mic.getProcessor()) {
+      void mic
+        .setProcessor(new LotusDenoiseProcessor(config))
+        .catch((e) => logger.warn("[lotus] denoise setProcessor failed", e));
+    }
+  };
+
+  const roomListeners = new Map<LivekitRoom, () => void>();
+  let rooms: LivekitRoom[] = [];
+
+  const sub = vm.livekitRoomItems$.subscribe((items) => {
+    const next = items.map((i) => i.livekitRoom);
+    rooms = next;
+    for (const [room, off] of roomListeners) {
+      if (!next.includes(room)) {
+        off();
+        roomListeners.delete(room);
+      }
+    }
+    for (const room of next) {
+      if (!roomListeners.has(room)) {
+        // Re-attach on every (re)publish — this is what makes denoise survive
+        // reconnects (A7), unlike the old getUserMedia patch.
+        const onPublished = (): void => apply(room);
+        room.localParticipant.on(
+          ParticipantEvent.LocalTrackPublished,
+          onPublished,
+        );
+        roomListeners.set(room, () =>
+          room.localParticipant.off(
+            ParticipantEvent.LocalTrackPublished,
+            onPublished,
+          ),
+        );
+        apply(room);
+      }
+    }
+  });
+
+  return () => {
+    sub.unsubscribe();
+    for (const off of roomListeners.values()) off();
+    roomListeners.clear();
+    for (const room of rooms) {
+      const mic = micOf(room);
+      if (mic?.getProcessor()) void mic.stopProcessor();
+    }
+  };
+}