feat(lotus): report remote screenshare audio to the host (cinny #277)

New fromWidget action io.lotus.screenshare_audio_state { present }: each
LivekitRoomAudioRenderer reports whether a remote participant's
ScreenShareAudio track is being received; the combined answer is sent to
the host on change, and cleared when a renderer unmounts. cinny uses it to
show "Mute Screenshare Audio" only when there is something to mute.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/lotus/lotusScreenshareAudio.test.ts

@@ -0,0 +1,59 @@
+/*
+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 { beforeEach, expect, test, vi } from "vitest";
+
+import { LotusWidgetActions } from "./lotusActions";
+import {
+  clearScreenshareAudio,
+  reportScreenshareAudio,
+  resetScreenshareAudioPresence,
+} from "./lotusScreenshareAudio";
+
+const send = vi.fn().mockResolvedValue({});
+
+vi.mock("../widget", () => ({
+  widget: {
+    api: { transport: { send: (...a: unknown[]): unknown => send(...a) } },
+  },
+}));
+
+const sent = (): unknown[] =>
+  send.mock.calls
+    .filter(([action]) => action === LotusWidgetActions.ScreenshareAudioState)
+    .map(([, data]) => data);
+
+beforeEach(() => {
+  resetScreenshareAudioPresence();
+  send.mockClear();
+});
+
+test("[cinny #277] reports presence only when the combined answer changes", () => {
+  reportScreenshareAudio("sfu-a", false);
+  reportScreenshareAudio("sfu-a", false);
+  reportScreenshareAudio("sfu-a", true);
+  reportScreenshareAudio("sfu-a", true);
+  reportScreenshareAudio("sfu-a", false);
+  expect(sent()).toEqual([
+    { present: false },
+    { present: true },
+    { present: false },
+  ]);
+});
+
+test("[cinny #277] any room with screenshare audio counts as present", () => {
+  reportScreenshareAudio("sfu-a", true);
+  reportScreenshareAudio("sfu-b", false);
+  expect(sent()).toEqual([{ present: true }]);
+  // A share is still playing in sfu-b after sfu-a's stops.
+  reportScreenshareAudio("sfu-b", true);
+  reportScreenshareAudio("sfu-a", false);
+  expect(sent()).toEqual([{ present: true }]);
+  // The renderer for sfu-b unmounts (call left): nothing is playing.
+  clearScreenshareAudio("sfu-b");
+  expect(sent()).toEqual([{ present: true }, { present: false }]);
+});