feat(onboarding): add agent-waiting step with simulated ping

src/features/onboarding/steps/step-agent-waiting.tsx

@@ -0,0 +1,23 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+import { useOnboarding } from "@onboardjs/react";
+import { simulateAgentPing } from "@/features/onboarding/onboarding.mock";
+
+export const StepAgentWaiting = () => {
+    const { next } = useOnboarding();
+    const started = useRef(false);
+
+    useEffect(() => {
+        if (started.current) return;
+        started.current = true;
+        simulateAgentPing().then(() => next());
+    }, [next]);
+
+    return (
+        <div className="flex flex-col items-center justify-center gap-2 h-full text-center">
+            <h1 className="text-xl font-semibold">Waiting for your agent</h1>
+            <p className="text-sm text-muted-foreground">Checking connectivity and database health...</p>
+        </div>
+    );
+};