On 4.0.3 a third-party plugin declaring `kinds: ["menu", "bar-widget"]` receives a scoped shell API whose `appLibrary` is `null`, so its Apps submenu is permanently empty.

Per `shell.qml:603`, a menu-kind plugin is supposed to receive it:

```qml
appLibrary: shell.manifestHasKind(manifest, "menu")
  ? shell.pluginAppLibraryFor(cacheKey, key) : null,
bar: shell.pluginBarStateFor(cacheKey, key),
```

## Evidence

Probing the injected `shell` object from inside the plugin, every 1.5 s for its whole lifetime:

```
shell=true pluginId=krall.switchboard appLib=null
bar=PluginBarStateApi_QMLTYPE_27(0x7f94...) idleCfg=yes barCfg=yes
```

- `appLibrary` is null from creation onward and never populated — not a startup race.
- `bar` — created by `pluginBarStateFor(cacheKey, key)` in the **same** `createObject` properties block — succeeds. So object creation itself is fine, and the API did come from `createScopedPluginShell` rather than the bar-entry path.
- The manifest carries `kinds: ["menu", "bar-widget"]`. It is precisely that `"menu"` kind that puts the plugin into `computePanelEntries` (which independently checks `Array.isArray(m.kinds)` and `indexOf("menu")`), so the plugin does reach the panel loader.
- Nothing after `createObject` reassigns `appLibrary`; `syncPluginApis` only refreshes `barConfig` and `idleConfig`.
- No QML warning is logged.

So the grant condition evaluates false for a plugin that appears to satisfy it. I could not isolate which branch fails without patching `shell.qml`, which is package-owned — hence an issue rather than a PR.

## Reproduction

Any third-party plugin with kind `"menu"` — e.g. [krall12/omarchy-switchboard](https://github.com/krall12/omarchy-switchboard). Its Apps list comes up empty on 4.0.3.

It worked on 4.0.2, where the panel loader injected the full shell (`shell.qml:630`):

```qml
if ("shell" in item) item.shell = shell
if ("manifest" in item) item.manifest = panelEntry.manifest
```

4.0.3 routes both through the new sandbox layer (`pluginShellFor` / `publicPluginManifest`), which is where the regression lives.

## Possibly related

The same sandbox change also strips `__sourceDir` from third-party manifests (`publicPluginManifest`, `shell.qml:316`). That is plausibly deliberate, but it silently breaks any plugin that resolves its own bundled scripts through the manifest — worth a note in the plugin API docs if so, since the failure mode is invisible (no warning, IPC still answers `ok`).

## Environment

- omarchy 4.0.3-1 (regressed from 4.0.2-1)
- quickshell 0.3.1-1
- Hyprland, single monitor