Same class of bug as cd982f2: 9878ab4 (extract FilesTab) also
removed 'let' declarations for capture/drag-drop state that's still
used by the inbox capture flow and CaptureDropOverlay:
captureDropActive, captureDropLabel, captureDragDepth,
lastCaptureDragOverAt, captureDragResetTimer,
dropRootValid, inboxDropValid
Without them, Svelte runtime throws ReferenceError on first render
('captureDropActive is not defined'), leaving the WebView empty.
Verified with headless render smoke: .app + .sidebar mount,
sidebar shows system views + workspace, welcome screen renders.
Rebuild embedded frontend bundle.
