### What happened

Running `omarchy plugin clone omarchy.bar` — a documented customization workflow — leaves the system with **no bar at all**. The cloned bar fails to load, and the intended fallback to the stock bar also fails, so nothing renders. It stays gone across `omarchy restart shell`.

The clone itself is unmodified at this point: the failure happens with a byte-for-byte copy of `shell/plugins/bar/Bar.qml`.

### Expected

Either the cloned bar loads and renders identically to the stock bar, or (if it can't load) the documented fallback in `shell.qml` puts `omarchy.bar` back on screen.

### Root cause

Two separate bugs stack up.

**1. A plugin bar can never satisfy `required property`.**

`shell/plugins/bar/Bar.qml` declares three required properties:

```qml
required property string omarchyPath      // :15
required property var barWidgetRegistry   // :17
required property var barConfig           // :22
```

The stock bar is instantiated from `defaultBarComponent` (`shell.qml:225`), which sets all three inline at construction — fine.

A plugin bar goes through `pluginBarLoader` (`shell.qml:246`) instead, which loads by URL and assigns the properties *afterwards*:

```qml
source: shell.activeBarId !== shell.defaultBarId ? shell.activeBarSourceUrl : ""
asynchronous: true
onLoaded: shell.configureBar(item, shell.activeBarManifest)
```

`Loader.source` has no way to supply required properties at creation, so instantiation fails before `configureBar()` (`shell.qml:214`) ever runs:

```
WARN scene: file:///home/john/.config/omarchy/plugins/john.bar/Bar.qml[15:3]: Required property omarchyPath was not initialized
WARN scene: file:///home/john/.config/omarchy/plugins/john.bar/Bar.qml[22:3]: Required property barConfig was not initialized
WARN scene: file:///home/john/.config/omarchy/plugins/john.bar/Bar.qml[17:3]: Required property barWidgetRegistry was not initialized
```

**2. The error handler throws, so the fallback never happens.**

`shell.qml:254`:

```qml
onStatusChanged: {
  if (status === Loader.Error) {
    var detail = errorString && errorString() ? errorString() : ""   // :256
    console.warn(...)
    shell.failedBarId = shell.activeBarId                            // :258
  }
}
```

`Loader` has no `errorString` member (that's `QQmlComponent`), so line 256 throws:

```
WARN scene: @shell.qml[256:-1]: ReferenceError: errorString is not defined
```

Line 258 never executes, so `failedBarId` stays `""`. `activeBarId` (`shell.qml:180`) therefore keeps resolving to the broken plugin bar, `defaultBarLoader` stays inactive (`shell.qml:240`), and the user is left with no bar — rather than the graceful degradation the code clearly intends.

### Steps to reproduce

1. On a stock install, run `omarchy plugin clone omarchy.bar`
   → "Cloned omarchy.bar to ~/.config/omarchy/plugins/<user>.bar and switched to <user>.bar"
2. The bar disappears immediately. `omarchy restart shell` does not bring it back.
3. `journalctl --user -e | grep Bar.qml` shows the three required-property warnings plus the `errorString` ReferenceError.

### Verified against main

Not just the installed version — I fetched both files from `basecamp/omarchy@main` and the code is identical, at the same line numbers (`Bar.qml:15,17,22` and `shell.qml:250,256`).

### Workaround

Relaxing the three declarations in the *clone* makes it load correctly, since `configureBar()` assigns all three post-load anyway:

```qml
property string omarchyPath: ""
property var barWidgetRegistry: null
property var barConfig: null
```

`barConfig` is already null-safe at its use site (`Util.isPlainObject(barConfig) ? barConfig : fallbackBarConfig`, `Bar.qml:375`). `barWidgetRegistry` is dereferenced unguarded at `Bar.qml:1584` (`root.barWidgetRegistry.widgets`), so it needs a guard to be safe during the window before `configureBar()` runs.

Bug 2 is worth fixing regardless of bug 1: any plugin bar that fails to load for any reason currently takes the whole bar down instead of falling back.

### System

| | |
|---|---|
| Omarchy | 4.0.1-2 |
| Hardware | Apple MacBook Pro 14" (M1 Pro, 2021), aarch64 (Asahi) |
| Kernel | 7.1.6-1-1-ARCH |
| Hyprland | 0.56.1 |
| Quickshell | 0.3.1 (Arch) |
| Qt | qt6-base 6.11.2-3 |