fix: implement stream playback cleaner structure

js/src/hooks/use-recording-mode.ts

@@ -0,0 +1,19 @@
+import { useState, useCallback } from "react";
+
+export type RecordingMode = "video" | "audio";
+
+const KEY = "llink:recording-mode";
+
+export function useRecordingMode(): [RecordingMode, (mode: RecordingMode) => void] {
+  const [mode, setModeState] = useState<RecordingMode>(() => {
+    const stored = localStorage.getItem(KEY);
+    return stored === "audio" ? "audio" : "video";
+  });
+
+  const setMode = useCallback((m: RecordingMode) => {
+    localStorage.setItem(KEY, m);
+    setModeState(m);
+  }, []);
+
+  return [mode, setMode];
+}