Fix post-auth session handoff flow

hooks/use-auth-handoff.ts

@@ -0,0 +1,60 @@
+'use client';
+
+import { useEffect, useRef } from 'react';
+
+const HANDOFF_TIMEOUT_MS = 10_000;
+
+type AuthSession = {
+  user?: {
+    id?: string;
+  };
+} | null;
+
+type UseAuthHandoffOptions = {
+  nextPath: string;
+  session: AuthSession;
+  isPending: boolean;
+  awaitingSession: boolean;
+  onTimeout: () => void;
+};
+
+export function useAuthHandoff({
+  nextPath,
+  session,
+  isPending,
+  awaitingSession,
+  onTimeout
+}: UseAuthHandoffOptions) {
+  const hasNavigatedRef = useRef(false);
+  const hasSession = Boolean(session?.user?.id);
+
+  useEffect(() => {
+    if (typeof window === 'undefined' || isPending || !hasSession || hasNavigatedRef.current) {
+      return;
+    }
+
+    hasNavigatedRef.current = true;
+    window.location.replace(nextPath);
+  }, [hasSession, isPending, nextPath]);
+
+  useEffect(() => {
+    if (typeof window === 'undefined' || !awaitingSession || hasSession || hasNavigatedRef.current) {
+      return;
+    }
+
+    const timeoutId = window.setTimeout(() => {
+      onTimeout();
+    }, HANDOFF_TIMEOUT_MS);
+
+    return () => {
+      window.clearTimeout(timeoutId);
+    };
+  }, [awaitingSession, hasSession, onTimeout]);
+
+  return {
+    isHandingOff: awaitingSession || (!isPending && hasSession),
+    statusText: awaitingSession
+      ? 'Establishing your session and opening the workspace...'
+      : null
+  };
+}