fix: list of streams glitching to top

This was due to real-time changes to items leading to scrolling to top.

Closes #123

js/src/hooks/use-stream-keyboard-nav.ts

@@ -13,9 +13,14 @@ export function useStreamKeyboardNav({
 }: UseStreamKeyboardNavOptions) {
   const [selectedIndex, setSelectedIndex] = useState<number | null>(null);
 
-  // Reset selection to first item when streams change or view mode switches
+  // Initialize selection when streams first load; clear if streams become empty.
+  // Do NOT reset on every Firestore update — that would scroll the list to the top.
   useEffect(() => {
-    setSelectedIndex(streams.length > 0 ? 0 : null);
+    setSelectedIndex((prev) => {
+      if (streams.length === 0) return null;
+      if (prev === null) return 0;
+      return prev;
+    });
   }, [streams.length]);
 
   useEffect(() => {