## What happened

Setting a custom bar plugin via `bar.id` in `~/.config/omarchy/shell.json` (the documented workflow behind `omarchy plugin clone omarchy.bar`) makes the bar disappear entirely — no exclusion zone, no widgets, nothing rendered. This reproduces with a **byte-for-byte unmodified copy** of the stock `Bar.qml`, so it's not specific to any customization of the bar's content.

## Expected

The bar plugin selected by `bar.id` should render just like the built-in bar.

## Steps to reproduce

1. `omarchy plugin clone omarchy.bar` (creates `~/.config/omarchy/plugins/<user>.bar/`, and adds `"id": "<user>.bar"` under `bar` in `shell.json`)
2. Don't even edit the clone — leave `Bar.qml` as copied.
3. Save `shell.json`. The bar plugin hot-reloads.
4. The bar vanishes: `hyprctl layers` shows no `omarchy-bar` namespace on any output, and no exclusion zone is reserved at the bar's edge.
5. Remove the `"id"` key from `bar` in `shell.json` (falling back to the built-in bar) → the bar reappears immediately, confirming the bar-plugin-switch path itself is broken, not the cloned content.

## Root cause (traced through `quickshell log`)

`shell/plugins/bar/Bar.qml` declares:

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

The **built-in** bar (`shell.qml`'s `defaultBarComponent`) sets these as literal property bindings at construction time, so the `required` check is satisfied immediately.

The **plugin/cloned** bar is loaded through `pluginBarLoader`, a `Loader { source: <url>; asynchronous: true }` (`shell.qml:246-261`). Its `onLoaded` handler calls `shell.configureBar(item, ...)`, which assigns `omarchyPath`/`barWidgetRegistry`/`barConfig` **imperatively, after the component is already constructed**. That's too late to satisfy QML's `required property` contract — `QQmlComponent::create()` (which is what a URL-sourced `Loader` uses internally) fails outright when a required property has no initial binding, so the loader's `status` becomes `Loader.Error` and the whole thing silently falls back.

This is visible in the log as:

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

## Second, masking bug

`shell.qml`'s own error handler for this case is itself broken, so the *real* failure never gets logged with useful detail:

```qml
// shell.qml:254-260
onStatusChanged: {
  if (status === Loader.Error) {
    var detail = errorString && errorString() ? errorString() : ""   // <-- `errorString` is not in scope here
    console.warn("bar option " + shell.activeBarId + " failed to load, falling back to " + shell.defaultBarId + ":", detail)
    shell.failedBarId = shell.activeBarId
  }
}
```

`errorString` isn't a property/method available in that scope (it's not `pluginBarLoader.errorString`), so this throws:

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

...instead of printing the actual load failure. This is what made the original problem hard to diagnose — there's no `console.warn("bar option ... failed to load")` line in the log at all, just the generic "Required property" warnings and this unrelated `ReferenceError`.

## Suggested fix

Either:
- Drop `required` from the three properties in `Bar.qml` (they're already documented as host-injected), or
- Have `pluginBarLoader` supply initial values through `Component.createObject(parent, {omarchyPath: ..., barWidgetRegistry: ..., barConfig: ...})` instead of `Loader.source` + post-hoc assignment, or
- Use a `Loader` with `sourceComponent` built from `Qt.createComponent(url)` plus `incubateObject` with an initial properties object (supports required properties).

Separately, fix the `errorString` reference at `shell.qml:256` (likely meant `pluginBarLoader.status === Loader.Error ? "component failed to load" : ""`, or capturing the component's own `errorString()` before assigning `source`).

## Evidence

`quickshell log` at the exact moment `bar.id` was set to a clone (`artem.bar`):

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

`hyprctl layers` confirms no `omarchy-bar` layer surface exists on any output while `bar.id` points at the clone; removing `bar.id` (falling back to the built-in bar) makes it reappear immediately with no other change. Screenshot showing both states (top: bar missing with `bar.id` set; bottom: bar present with `bar.id` removed) will be attached to this issue.

## System details

```
$ omarchy version
4.0.2-1

$ quickshell --version
Quickshell 0.3.1 (revision , distributed by Arch Linux)

$ uname -a
Linux nb01 7.1.9-arch1-2 #1 SMP PREEMPT_DYNAMIC Fri, 21 Aug 2026 22:18:59 +0000 x86_64 GNU/Linux

GPU: Intel Corporation Raptor Lake-P [UHD Graphics] (rev 04), i915 driver
```