feat: add voice mode support via mic passthrough to container

Enables Claude Code's /voice command inside Docker containers by
capturing microphone audio in the Tauri webview and streaming it
into the container via a FIFO pipe.

Container: fake rec/arecord shims read PCM from a FIFO instead of
a real mic. Audio bridge exec writes PCM from Tauri into the FIFO.
Frontend: getUserMedia() + AudioWorklet captures 16kHz mono PCM
and streams it to the container via invoke("send_audio_data").
UI: "Mic Off/On" toggle button in the terminal view.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/public/audio-capture-processor.js

@@ -0,0 +1,17 @@
+class AudioCaptureProcessor extends AudioWorkletProcessor {
+  process(inputs, outputs, parameters) {
+    const input = inputs[0];
+    if (input && input.length > 0 && input[0].length > 0) {
+      const samples = input[0]; // Float32Array, mono channel
+      const int16 = new Int16Array(samples.length);
+      for (let i = 0; i < samples.length; i++) {
+        const s = Math.max(-1, Math.min(1, samples[i]));
+        int16[i] = s < 0 ? s * 0x8000 : s * 0x7FFF;
+      }
+      this.port.postMessage(int16.buffer, [int16.buffer]);
+    }
+    return true;
+  }
+}
+
+registerProcessor('audio-capture-processor', AudioCaptureProcessor);