[z1pp090]

Problem

The toolbar volume icon shows the muted icon while the default output device is playing
audio normally. Windows reports the device as default, unmuted and at 100%, but
@seelen/tb-media-popup keeps drawing IoVolumeMuteOutline until Seelen UI is restarted.

Reproduced on 2.8.2 (Windows 11 26200, bluetooth speaker):

1. Play audio on a bluetooth output device, everything looks right.
2. Turn the bluetooth radio off and on again, or power-cycle the speaker, so the endpoint
   disappears and comes back.
3. The device reconnects and audio works, but the toolbar icon stays muted. Restarting
   seelen-ui is the only way to recover it.

Root cause

Two separate bugs that compound each other.

1. DefaultDeviceChanged can clear every default flag.
IMMNotificationClient::OnDefaultDeviceChanged can report a device that DevicesManager has
not loaded yet, which happens routinely with bluetooth endpoints that are still being
enumerated. The handler then walks the map comparing ids:

devices.for_each(|(_, device)| {
    if *role == eMultimedia {
        device.is_default_multimedia = device.id == *device_id;
    }
});

Nothing matches, so the flag is cleared on every device and set on none. From that point on
the manager reports no default device at all.

2. "no default device" is rendered as "muted".
mediaStep defaults muted to true when there is no default device:

const { volume = 0, muted: isMuted = true } = defaultOutputDevice || {};

and the plugin template starts with return isMuted ? icon("IoVolumeMuteOutline") : ..., so a
device the user actually muted and a device the manager has lost are drawn with the exact same
icon. The toolbar reports a mute that does not exist.

Fix

• application.rs: when the reported default id is not in the map, load that device first, so
  the flags always land on a real device.
• scopes.svelte.ts: default muted to false. volume already defaults to 0, which
  renders the distinct "no output" icon, so the two states stay visually different.

Both isMuted and inputIsMuted are changed for consistency.

Notes

This may also be the underlying cause of #1590 ("nothing in the toolbox when I connect to my
bluetooth headset"): once no device is flagged as default, defaultOutput is undefined and
the media popup has nothing to render.

I could not build locally (no Rust toolchain on the machine where this was diagnosed), so the
Rust change is written against master and relies on CI for cargo fmt/clippy/test. The
analysis and the reproduction above are from a running 2.8.2 install.

[z1pp090]

Friendly ping on this one. It has been open since Aug 28 with no conflicts (mergeable: true) and the diff is small -- 19 added lines across 3 files, no API changes.

The fix is in two parts: OnDefaultDeviceChanged no longer clears every is_default_* flag when it receives a device the manager has not enumerated yet (routine with Bluetooth endpoints), and mediaStep no longer renders "no default device" as "muted".

Reproducible on 2.8.2 by power-cycling a Bluetooth speaker: audio comes back, the toolbar icon stays muted until seelen-ui is restarted.

Happy to rebase, split it into two commits, or adjust the approach if you would rather handle the missing-device case elsewhere.