After 9878ab4 moved file-preview state into FilesTab, App.svelte still
references previewItem/previewContent/previewLoading/previewError in
two places that were not migrated:
- openTrashPreview() (trash file preview flow, ~line 1334)
- {#if previewItem} <FilePreviewModal ...> block (~line 3563)
Without these 'let' bindings, vite-plugin-svelte warned
'previewError is not defined' and the Svelte runtime threw a
ReferenceError on first render, leaving the WebView empty.
Restore the four 'let' declarations in App.svelte (kept here because
trash lives outside FilesTab) and rebuild the embedded frontend bundle.