## What happened

Cloning the built-in bar plugin (`omarchy plugin clone omarchy.bar`) and switching to it (`omarchy bar use <cloned-id>`) results in a **completely invisible bar** — no widgets, no background, nothing rendered — even with a totally unmodified clone (zero edits). Confirmed by cloning fresh into a throwaway id and switching to it with no changes made.

## What I expected

The cloned bar to render identically to the stock bar (that's the documented purpose of `omarchy plugin clone` for the `bar` kind — customize height/behavior/etc. and keep it working).

## Root cause (traced in shell.qml)

In `/usr/share/omarchy/shell/shell.qml`, the stock bar is instantiated through `defaultBarComponent`, which explicitly binds the bar's required properties inline:

```qml
barWidgetRegistry: shell.barWidgetRegistry
barConfig: shell.barConfig
shell: shell
manifest: shell.barManifestFor(shell.defaultBarId)
```

But a custom/cloned `bar`-kind plugin goes through a different loader, `pluginBarLoader`, which just does a bare dynamic load with no property injection:

```qml
Loader {
  id: pluginBarLoader
  active: !shell.pluginReloading && shell.activeBarId !== shell.defaultBarId && shell.activeBarSourceUrl !== ""
  source: shell.activeBarId !== shell.defaultBarId ? shell.activeBarSourceUrl : ""
  asynchronous: true
  onLoaded: shell.configureBar(item, shell.activeBarManifest)
  ...
}
```

Since `Bar.qml`'s root `Item` declares `omarchyPath`, `barWidgetRegistry`, and `barConfig` as `required property`, and QML only allows required properties to be satisfied at object-creation time (a `Loader.source`-based load can't pass initial properties the way `createObject(parent, {props})` can), the component fails to initialize correctly. `shell.configureBar(item, ...)` runs afterward, but that's too late for `required property`.

Symptom in `journalctl --user` when this happens:

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

That last line is a second, separate bug: `pluginBarLoader`'s own `onStatusChanged` handler (shell.qml ~line 256) references a bare `errorString` that isn't defined in scope, so whatever the real `Loader.Error` message would have been gets swallowed by a `ReferenceError` instead of being logged.

## Steps to reproduce

```bash
omarchy plugin clone omarchy.bar   # make zero edits
# bar is now invisible
omarchy bar use omarchy.bar        # reverts fine, confirms it's not monitor/theme state
```

## System

- Omarchy 4.0.0-1
- Hyprland 0.56.2-1
- quickshell-git 0.3.0.r20.g28771c7-2
- CPU: 12th Gen Intel Core i9-12900H
- GPU: Intel Iris Xe (integrated) + NVIDIA GeForce RTX 3070 Ti Laptop (hybrid graphics)

## Impact

Blocks the documented "clone the bar to customize it" workflow entirely for anything that lives in the bar's root component (height, auto-hide behavior, exclusion zone, etc.) — not just for one specific customization. Individual bar-*widget* clones (`omarchy plugin clone omarchy.workspaces` etc.) are on a different, unaffected code path and still work fine.