Unsupported microphone sample format in Voice dictation experimental

### Short summary

Test mic in Voice dictation fails with error Unsupported microphone sample format

### Affected version or release

v0.2.23

### Installation context

Installed on Windows 11 Enterprise

### What happened?

Unable to get voice dictation experimental mode working on windows 11.
Error message on Test Mic: Unsupported microphone sample format
Error message when using in Home: No speech detected - Try speaking a little close to the microphone

Microphone confirmed works in general sound settings in windows
Microphone access provided and transcription model downloaded.
Tested both system default Input device and specific one used.

### Steps to reproduce

1. Enable voice dictation in Experimental menu
2. Go to voice dictation menu
3. Download transcription model
4. Click test mic and get error
5. Test from Home and get no results

### Expected behavior

Test mic should indicate the voice was captured successfully and voice dictation should work in home.

### Additional context

github-app.log contains the following from testing mic and attempted usage in home
```
2026-06-03T06:15:08.958179Z INFO github_app::voice: Testing voice input device input_device_id="Headset Microphone (Poly Blackwire 3320 Series)"
2026-06-03T06:15:09.968293Z DEBUG github_app::websocket: received message text={"type":"set_app_activity","visible":true,"focused":true}
2026-06-03T06:15:09.970335Z DEBUG github_app::websocket: received message text={"type":"set_app_activity","visible":true,"focused":false}
2026-06-03T06:15:46.866830Z DEBUG github_app::websocket: received message text={"type":"set_app_activity","visible":true,"focused":false}
2026-06-03T06:15:46.892100Z DEBUG github_app::websocket: received message text={"type":"set_app_activity","visible":true,"focused":true}
2026-06-03T06:15:54.610087Z INFO github_app::voice: Starting voice transcription session model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3 sample_rate=16000 channels=1 bits_per_sample=16
2026-06-03T06:15:54.649125Z INFO github_app::voice: Resolving voice transcription model model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.649143Z INFO github_app::voice: Resolved voice transcription model model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.649145Z INFO github_app::voice: Checking whether voice model is downloaded model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.649414Z INFO github_app::voice: Starting native voice audio capture input_device=Headset Microphone (Poly Blackwire 3320 Series) source_rate=16000 channels=1 sample_format=U8
2026-06-03T06:15:54.649866Z INFO github_app::voice: Voice model is downloaded model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.649873Z INFO github_app::voice: Checking whether voice model is loaded model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.650015Z INFO github_app::voice: Voice model is already loaded model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.650023Z INFO github_app::voice: Creating live transcription session model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.650027Z INFO github_app::voice: Starting live transcription session model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.698226Z INFO github_app::voice: Started live transcription session model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.698235Z INFO github_app::voice: Opening live transcription stream model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.698240Z INFO github_app::voice: Opened live transcription stream session_id=005b9117-e626-45af-9681-2dc3c436ce6f model_alias=nemotron-speech-streaming-en-0.6b-generic-cpu:3
2026-06-03T06:15:54.698307Z INFO github_app::voice: Voice audio append task finished session_id=005b9117-e626-45af-9681-2dc3c436ce6f appended_frames=0
2026-06-03T06:15:56.071186Z INFO github_app::voice: Stopping voice transcription session session_id=005b9117-e626-45af-9681-2dc3c436ce6f
2026-06-03T06:15:56.071201Z INFO github_app::voice: Stopping native voice audio capture
2026-06-03T06:15:56.072316Z INFO github_app::voice: Live voice transcription stream stopped session_id=005b9117-e626-45af-9681-2dc3c436ce6f
```