Volume control stops working when Bluetooth speaker is connected

### Compositor

Niri

### Distribution

Other (specify below)

### If Other, please specify

EndeavourOS

### Select your Installation Method

DankInstaller

### Was this your original Installation method?

Yes

### If no, specify

_No response_

### dms doctor -vC

Click to expand
## DMS Doctor Report

**System**
- [ok] Operating System: EndeavourOS
- ID: endeavouros, Version: rolling, Arch: amd64
- [ok] Architecture: amd64
- [ok] Display Server: Wayland
- WAYLAND_DISPLAY=wayland-1

**Versions**
- [ok] DMS CLI: dms v1.4.6
- /usr/bin/dms
- [ok] Quickshell: Quickshell 0.3.0 (revision , distributed by Arch Linux)
- /usr/bin/qs
- [ok] DMS Shell: v1.4.6
- /usr/share/quickshell/dms

**Installation**
- [ok] DMS Configuration: Found
- /usr/share/quickshell/dms
- [ok] shell.qml: Present
- /usr/share/quickshell/dms/shell.qml
- [info] Install Type: System package
- /usr/share/quickshell/dms

**Compositor**
- [ok] niri: 26.04
- /usr/bin/niri
- [info] Active: niri
- [ok] Background Blur: Supported
- Compositor supports ext-background-effect-v1

**Quickshell Features**
- [ok] Polkit: Available
- Authentication prompts
- [ok] IdleMonitor: Available
- Idle detection
- [ok] IdleInhibitor: Available
- Prevent idle/sleep
- [ok] ShortcutInhibitor: Available
- Allow shortcut management (niri)
- [ok] BackgroundBlur: Available
- Background blur API support in Quickshell

**Optional Features**
- [ok] accountsservice: Available
- User accounts
- [ok] power-profiles-daemon: Available
- Power profile management
- [ok] logind: Available
- Session management
- [ok] cups-pk-helper: Available
- Printer management
- [info] I2C/DDC: No monitors detected
- External monitor brightness control
- [ok] qt6-imageformats: Installed (1 formats)
- Formats: GIF (/usr/lib/qt6/plugins/imageformats:/usr/lib64/qt6/plugins/imageformats)
- [ok] kimageformats: Installed (4 formats)
- Formats: AVIF, HEIF, JXL, EXR (/usr/lib/qt6/plugins/imageformats:/usr/lib64/qt6/plugins/imageformats)
- [ok] Terminal: ghostty
- [ok] Network: NetworkManager
- NetworkManager present. Using NM API.
- [ok] matugen: Installed
- Dynamic theming
- [ok] dgop: Installed
- System monitoring
- [ok] cava: Installed
- Audio visualizer
- [info] khal: Not installed
- Calendar events
- [info] danksearch: Not installed
- File search
- [info] fprintd: Not installed
- Fingerprint auth

**Config Files**
- [ok] settings.json: Present
- /home/agustin/.config/DankMaterialShell/settings.json
- [info] clsettings.json: Not yet created
- /home/agustin/.config/DankMaterialShell/clsettings.json
- [info] plugin_settings.json: Not yet created
- /home/agustin/.config/DankMaterialShell/plugin_settings.json
- [ok] session.json: Present
- /home/agustin/.local/state/DankMaterialShell/session.json
- [ok] dms-colors.json: Present
- /home/agustin/.cache/DankMaterialShell/dms-colors.json

**Services**
- [ok] dms.service: enabled, active
- [ok] greetd: enabled

**Environment**
- [info] QT_QPA_PLATFORMTHEME: Not set
- [info] QS_ICON_THEME: Not set

---
**Summary:** 0 error(s), 0 warning(s), 31 ok

### Description

When I connect a Bluetooth speaker, the volume control in the bar stops working. Moving the slider does nothing. The only thing that works is the per-app control that shows up in the audio menu (like "Chrome: Playback").

As soon as I disconnect the Bluetooth device, the volume control works fine again.

### Expected Behavior

The volume slider should control the Bluetooth speaker, just like it does with the built-in audio

### Steps to Reproduce

1. Connect a Bluetooth speaker
2. Try to adjust the volume using the bar's volume slider
3. The slider moves but the volume doesn't change

### Error Messages/Logs

_No response_

### Screenshots/Recordings

_No response_

Start at the bar's volume slider and the audio menu's device controls, reproducing the issue with a Bluetooth speaker connected on Niri. Compare the failing main slider with the working per-app control, then verify that the slider changes the Bluetooth speaker volume while built-in audio continues to work after the fix.

Written by the indexing model from the issue text.