chore: apply oxlint fix-suggestions (unused imports + useless fragments)

Scoped to only `no-unused-vars` and `react/jsx-no-useless-fragment` —
the safe subset of --fix-suggestions. Primary changes:

- Remove unused named imports from statements
- Remove unused default/type imports entirely
- Collapse `<><Single/></>` fragments to `<Single/>`

Verified clean: typecheck + format + lint all green.

packages/app/src/components/file-explorer-pane.tsx

@@ -21,7 +21,6 @@ import {
   Download,
   MoreVertical,
   RotateCw,
-  X,
 } from "lucide-react-native";
 import { getFileIconSvg } from "@/components/material-file-icons";
 import { LoadingSpinner } from "@/components/ui/loading-spinner";