### What happened

`omarchy plugin clone omarchy.bar` is documented as the supported way to customize the status bar. But the clone it produces cannot actually load as a third-party plugin, with zero edits, because the shipped `Bar.qml` declares its host-injected properties as `required`:

```qml
// shell/plugins/bar/Bar.qml
required property string omarchyPath
required property var barWidgetRegistry
required property var barConfig
```

This works for the built-in bar because it's instantiated inline in `shell.qml` as a `Component` with all three bound directly at construction time:

```qml
Component {
  id: defaultBarComponent
  Bar {
    omarchyPath: shell.omarchyPath
    barWidgetRegistry: shell.barWidgetRegistry
    barConfig: shell.barConfig
    shell: shell
    manifest: shell.barManifestFor(shell.defaultBarId)
  }
}
```

A cloned bar, however, is loaded by `pluginBarLoader`, a plain `Loader { source: url }`. Quickshell can only assign properties to that item *after* it's constructed (via `shell.configureBar(item, ...)` in `onLoaded`), and QML's `required` contract demands they be set atomically at construction. Any bar cloned this way — even completely unedited — fails to load.

### Steps to reproduce

1. `omarchy plugin clone omarchy.bar`
2. `omarchy restart shell`
3. The bar disappears (see basecamp/omarchy#10324 for why the fallback-to-stock-bar path also silently fails here, compounding this).
4. Quickshell's log shows:
   ```
   WARN scene: file:///home/<user>/.config/omarchy/plugins/<user>.bar/Bar.qml[15:3]: Required property omarchyPath was not initialized
   WARN scene: file:///home/<user>/.config/omarchy/plugins/<user>.bar/Bar.qml[17:3]: Required property barWidgetRegistry was not initialized
   WARN scene: file:///home/<user>/.config/omarchy/plugins/<user>.bar/Bar.qml[22:3]: Required property barConfig was not initialized
   ```

### Expected

`omarchy plugin clone omarchy.bar` produces a bar that loads and renders identically to the stock bar, ready for further customization — this is the whole point of the clone workflow (see the plugin docs: "Clone a built-in Omarchy shell plugin into your own config").

### Actual

The freshly cloned, unedited bar fails to load at all.

### System

- Omarchy: 4.0.0-1 (stable channel)
- Hyprland: 0.56.2
- Quickshell: 0.3.0 (quickshell-git AUR)
- `uname -a`: Linux 7.1.8-arch1-3 x86_64

### Suggested fix

Either:
- Change the shipped `Bar.qml`'s three host-injected properties from `required property` to plain `property` with safe defaults (e.g. `property string omarchyPath: ""`, `property var barWidgetRegistry: ({ widgets: ({}) })`, `property var barConfig: null`), matching how `manifest` and `shell` are already declared as plain (non-required) properties right below them; or
- Have `pluginBarLoader` construct the item with initial properties supplied atomically (e.g. `Loader.setSource(url, {omarchyPath: ..., barWidgetRegistry: ..., barConfig: ...})` or `Component.createObject(parent, {...})`) instead of relying on post-construction assignment in `onLoaded`.

The first option is the smaller, more contained fix and is what I applied locally to unblock a custom-bar clone.