fix: handle MFA binding skip during registration submit

The registration flow hit a 422 on /api/experience/submit when MFA
policy is UserControlled. Adds the same trySubmit + skipMfaBinding
pattern already used in the sign-in flow — Logto confirms mfa-skipped
works for both SignIn and Register interaction events.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/sign-in/src/experience-api.ts

@@ -180,7 +180,19 @@ export async function completeRegistration(
   const verifiedId = await verifyCode(email, verificationId, code);
   await addProfile('password', password);
   await identifyUser(verifiedId);
-  return submitInteraction();
+
+  const result = await trySubmit();
+  if (result.ok) return result.redirectTo;
+
+  // MFA not enrolled, UserControlled policy — skip the binding prompt
+  if (result.status === 422 && result.code.includes('mfa')) {
+    await skipMfaBinding();
+    const retry = await trySubmit();
+    if (retry.ok) return retry.redirectTo;
+    throw new Error(retry.message);
+  }
+
+  throw new Error(result.message);
 }
 
 // --- Forgot Password ---