feat: enable marketing site registration and launch-prompt preservation (T12)

vibn-frontend/marketing/components/new-site/index.tsx

@@ -2354,7 +2354,7 @@ function Closing() {
 
         <div className="closing-cta">
           <div className="row">
-            <a href="Beta Signup.html" className="btn btn-primary">
+            <a href="/auth?new=1" className="btn btn-primary">
               Request invite <Arrow />
             </a>
             <a href="#how" className="btn btn-ghost">
@@ -2598,6 +2598,17 @@ function LaunchModal({ prompt, onClose }) {
     return () => window.removeEventListener("keydown", onKey);
   }, [onClose]);
 
+  // Preserve prompt for onboarding seeding (T12)
+  useEffect(() => {
+    if (typeof window !== "undefined" && prompt) {
+      try {
+        localStorage.setItem("vibn:firstName", prompt);
+      } catch (err) {
+        console.error("Failed to save hero prompt to localStorage:", err);
+      }
+    }
+  }, [prompt]);
+
   const [step, setStep] = useState(0);
   useEffect(() => {
     if (step >= 4) return undefined;
@@ -2605,6 +2616,17 @@ function LaunchModal({ prompt, onClose }) {
     return () => clearTimeout(t);
   }, [step]);
 
+  const [redirectCount, setRedirectCount] = useState(3);
+  useEffect(() => {
+    if (step < 4) return undefined;
+    if (redirectCount <= 0) {
+      window.location.href = "/auth";
+      return undefined;
+    }
+    const t = setTimeout(() => setRedirectCount(redirectCount - 1), 1000);
+    return () => clearTimeout(t);
+  }, [step, redirectCount]);
+
   return (
     <div className="modal-backdrop" onClick={onClose}>
       <style>{`
@@ -2693,9 +2715,50 @@ function LaunchModal({ prompt, onClose }) {
           ))}
         </div>
 
-        <div className="modal-foot">
-          No homework · No setup · No new tools to learn
-        </div>
+        {step === 4 ? (
+          <div
+            className="modal-actions"
+            style={{
+              marginTop: "24px",
+              display: "flex",
+              flexDirection: "column",
+              gap: "12px",
+              alignItems: "center",
+            }}
+          >
+            <a
+              href="/auth"
+              className="btn btn-primary"
+              style={{
+                width: "100%",
+                height: "48px",
+                display: "inline-flex",
+                alignItems: "center",
+                justifyContent: "center",
+                gap: "8px",
+                fontSize: "15px",
+                fontWeight: "600",
+                textDecoration: "none",
+              }}
+            >
+              Launch Your Workspace <Arrow size={14} />
+            </a>
+            <span
+              style={{
+                fontSize: "11px",
+                color: "var(--fg-faint)",
+                fontFamily: "var(--font-mono)",
+                letterSpacing: "0.04em",
+              }}
+            >
+              Redirecting to registration in {redirectCount}s...
+            </span>
+          </div>
+        ) : (
+          <div className="modal-foot">
+            No homework · No setup · No new tools to learn
+          </div>
+        )}
       </div>
     </div>
   );