fix(lotus): capture the microphone mono — stereo interfaces published left-only on Firefox

audioCaptureDefaults set no channelCount, so Firefox captured a 2-channel
audio interface (Scarlett Solo, one XLR mic on input 1) as stereo and,
with browser audio processing off (the ML denoise tier), published it as
is: peers heard the speaker in the left ear only. Chrome downmixes such
captures itself, which is why it only showed on Firefox. Request
channelCount: 1 for mic capture; screenshare audio is captured separately
and is unaffected. Tested. Bumps to 0.25.0-lotus.3.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/lotus/lotusAudioConstraints.test.ts

@@ -88,6 +88,16 @@ afterEach(() => {
 });
 
 describe("[lotus] audio-capture URL param overrides", () => {
+  test("mic capture is always requested mono (stereo interfaces on Firefox published L-only)", () => {
+    getUrlParams.mockReturnValue({
+      echoCancellation: false,
+      noiseSuppression: false,
+      autoGainControl: false,
+    });
+    createRoom();
+    expect(capturedAudioDefaults()).toMatchObject({ channelCount: 1 });
+  });
+
   test("with params defaulted to true, the Settings govern (upstream behaviour)", () => {
     getUrlParams.mockReturnValue({
       echoCancellation: true,