Huddle: speaker (audio output) selector is inert — cannot enable the speaker or change output device (Desktop 0.5.14, Windows 11)

## Summary

In a huddle, the speaker (audio output) selector in the huddle controls does not work: the selection cannot be changed, and turning the speaker on has no effect. The microphone/mute control behaves normally — the problem is specific to audio output.

The practical effect is that the huddle is one-way: the agent's spoken replies are never heard, because there is no working way to enable or route audio output.

## Steps to reproduce

1. Open a huddle in Buzz Desktop (reproduced in a 1:1 huddle between a human and a managed agent).
2. Open the huddle audio controls and try to enable the speaker.
3. Try to pick a different output device from the speaker selector.

## Expected

- Toggling the speaker enables audio output for the huddle.
- Picking a different output device in the selector switches playback to that device and the selection sticks.

## Actual

- The speaker cannot be activated.
- The selector's choice cannot be changed.

## Environment

- Buzz Desktop 0.5.14 (Windows installer build, `C:\Users\Gus\AppData\Local\Buzz`)
- Windows 11 Home, 10.0.26200
- Self-hosted relay

## Notes

Reported from live use, not from source inspection — I did not have a checkout to point at the responsible code, so there is no line reference here.

I searched open and closed issues for `speaker`, `audio output`, `device picker`, `microphone device`, `setSinkId`, `unmute`, and `huddle controls` and found no existing report of this. The closest is #3118 (huddle `mediaDevices` access crashes the app when `navigator.mediaDevices` is undefined), which is a different failure — here the app does not crash, the control is simply inert.