fix(voice): 麦克风约束兜底——WKWebView 不认高级约束("Invalid constraint")退 {audio:true}

原生壳(Wails WKWebView)的 getUserMedia 不认 channelCount/echoCancellation 等高级约束,
抛 "Invalid constraint"。先试高级约束(浏览器更好),失败退回最简 {audio:true}(最兼容)。
配合上一提交的 .app 打包+NSMicrophoneUsageDescription,原生壳麦克风打通。

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

sundynix-desktop/frontend/src/lib/voice.ts

@@ -201,9 +201,16 @@ export class VoiceClient {
     if (!navigator.mediaDevices?.getUserMedia) {
       throw new Error("此窗口暂不支持麦克风（原生壳需授权/安全上下文）。用浏览器打开 localhost:5173 可直接说话。");
     }
-    const stream = await navigator.mediaDevices.getUserMedia({
+    // 先试带回声消除等约束（浏览器更好），WKWebView（原生壳）不认高级约束会抛 "Invalid constraint"，
-      audio: { channelCount: 1, echoCancellation: true, noiseSuppression: true },
+    // 退回最简 {audio:true}（最兼容；多数实现默认已开回声消除）。
-    });
+    let stream: MediaStream;
+    try {
+      stream = await navigator.mediaDevices.getUserMedia({
+        audio: { echoCancellation: true, noiseSuppression: true, channelCount: 1 },
+      });
+    } catch {
+      stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+    }
     this.micStream = stream;
     const ctx = new AudioContext();
     this.micCtx = ctx;