### Summary
The Bluetooth widget completely disappears from the Omarchy status bar when Bluetooth is turned off via the UI switch. This leaves the user with no way to turn Bluetooth back on using the UI.

### Expected Behaviour
When turning off Bluetooth using the status bar toggle, the widget should remain visible but display a "Turned Off" or "Disabled" state. Clicking the toggle again should turn the Bluetooth adapter back on.

### Actual Behaviour
When Bluetooth is toggled off, the entire widget vanishes from the shell. The only way to restore Bluetooth functionality is via the terminal (e.g. `rfkill unblock bluetooth` or `omarchy bluetooth power on`).

### Steps to Reproduce
1. Open the Omarchy status bar menus.
2. Ensure the Bluetooth widget is visible.
3. Click the toggle switch on the Bluetooth widget to turn it off.
4. The widget immediately disappears from the bar and cannot be recovered via the UI.

### System Details
- **OS**: Omarchy Linux (Kernel: 7.1.8-arch1-3)
- **Omarchy Version**: 4.0.0-1

### Cause of Bug
When turning off Bluetooth via the Omarchy UI toggle switch, it calls `omarchy-bluetooth-power off`, which soft blocks the adapter via `rfkill`. This causes the adapter to completely disappear from the BlueZ daemon, meaning the `adapter` property becomes `null` in `Quickshell.Bluetooth`.

Because the built-in `omarchy.bluetooth` widget (`Panel.qml`) has a strict visibility condition tied to the adapter (`visible: adapter !== null`), the widget hides itself when `adapter` becomes `null`. 

**The code that didn't work properly in `Panel.qml`:**
```qml
  visible: adapter !== null

  // ... (inside toggleBluetooth)
  function toggleBluetooth() {
    if (!adapter) return
    Quickshell.execDetached(["omarchy-bluetooth-power", adapter.enabled ? "off" : "on"])
  }
```

### Fix for Bug
The fix involves ensuring the widget stays visible even when the adapter disappears (due to being soft-blocked), and updating the UI text/icons and the toggle logic to handle a `null` adapter state. 

Here are the fixes to apply in `Panel.qml`:

1. Change panel visibility to always true:
```qml
  visible: true
```

2. Update `toggleBluetooth()` to send the `on` signal when the adapter is missing:
```qml
  function toggleBluetooth() {
    if (!adapter) {
      Quickshell.execDetached(["omarchy-bluetooth-power", "on"])
      return
    }
    Quickshell.execDetached(["omarchy-bluetooth-power", adapter.enabled ? "off" : "on"])
  }
```

3. Update the `icon` and `heroStatusText` to fallback to disabled visuals when `!adapter`:
```qml
  readonly property string icon: {
    if (!adapter) return "󰂲"
    if (!adapter.enabled) return "󰂲"
    // ...
  }
```

*(Reporting on behalf of a user using the Antigravity assistant)*