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/runtime/host-runtime.ts

@@ -1,4 +1,4 @@
-import { useSyncExternalStore, useCallback, useMemo } from "react";
+import { useSyncExternalStore, useMemo } from "react";
 import AsyncStorage from "@react-native-async-storage/async-storage";
 import equal from "fast-deep-equal/es6";
 import {