### What happened

`omarchy plugin clone omarchy.bar` produces a bar plugin that **cannot be instantiated**.
After `omarchy bar use <clone-id>` the bar never appears — the `omarchy-bar` layer is
absent from `hyprctl layers`, leaving only `omarchy-background`. The shell itself keeps
running.

Journal shows:

```
WARN scene: file:///home/…/.config/omarchy/plugins/<id>/Bar.qml[22:3]: Required property barConfig was not initialized
WARN scene: file:///home/…/.config/omarchy/plugins/<id>/Bar.qml[15:3]: Required property omarchyPath was not initialized
WARN scene: file:///home/…/.config/omarchy/plugins/<id>/Bar.qml[17:3]: Required property barWidgetRegistry was not initialized
WARN scene: @shell.qml[256:-1]: ReferenceError: errorString is not defined
```

### What I expected

A freshly cloned bar renders identically to the built-in one, since `omarchy plugin clone`
advertises itself as the supported way to customize a built-in plugin.

### Steps to reproduce

```bash
omarchy plugin clone omarchy.bar     # also switches to the clone
omarchy restart shell
hyprctl layers | grep omarchy-bar    # no bar layer
```

Recover with `omarchy bar use omarchy.bar && omarchy restart shell`.

### Root cause

The two bar load paths in `shell/shell.qml` are not equivalent.

The **built-in** bar is instantiated by a `Component` that supplies the required properties
**at creation time**:

```qml
Component {
  id: defaultBarComponent
  Bar {
    omarchyPath: shell.omarchyPath
    barWidgetRegistry: shell.barWidgetRegistry
    barConfig: shell.barConfig
    …
  }
}
```

A **third-party** bar is loaded from a URL, which cannot supply any initial property, and is
configured only afterwards in `onLoaded`:

```qml
Loader {
  id: pluginBarLoader
  source: shell.activeBarSourceUrl
  onLoaded: shell.configureBar(item, shell.activeBarManifest)
}
```

`configureBar` sets the same three properties — but `plugins/bar/Bar.qml` declares them as
`required property`, so QML refuses to construct the object before `onLoaded` ever runs.
Since `omarchy plugin clone` copies `Bar.qml` verbatim, every cloned bar hits this.

The secondary `ReferenceError: errorString is not defined` comes from the error branch in
the same Loader (`errorString && errorString()`), which then can't report the real failure.

### Suggested fixes

Either would do:

1. Drop `required` from `omarchyPath`, `barWidgetRegistry` and `barConfig` in
   `plugins/bar/Bar.qml`, giving them defaults — `configureBar` already assigns them on load.
2. Or have `pluginBarLoader` use `setSource(url, { … })` so the required properties are
   provided at creation, matching the built-in path.

I'm currently using (1) as a local patch and the cloned bar works correctly.

There is also a leftover IPC collision worth a look: the cloned bar still registers
`IpcHandler { target: "omarchy.bar" }`, producing
`Handler was registered but will not be used because another handler is registered for target omarchy.bar`.

### System

| | |
|---|---|
| Omarchy | 4.0.2-1 |
| Kernel | 7.1.9-arch1-2 |
| CPU | 12th Gen Intel Core i7-12700H |
| GPU | Intel Alder Lake-P GT2 [Iris Xe] + NVIDIA GA107M [RTX 3050 Ti Mobile] |
| Hyprland | 0.56.2 |
| Quickshell | 0.3.1 (Arch) |

Note: `omarchy debug --no-sudo --print` is not available in 4.0.2-1 (`Unknown Omarchy
command`), so the details above were collected manually.