fix: skip MFA binding prompt for UserControlled policy during sign-in

Logto returns 422 with an MFA recommendation when policy is
UserControlled. Call POST /profile/mfa/mfa-skipped to skip the
binding prompt, then re-submit. Users who already have MFA enrolled
still get the TOTP verification flow.

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

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

@@ -71,20 +71,42 @@ export class MfaRequiredError extends Error {
   }
 }
 
+async function trySubmit(): Promise<{ ok: true; redirectTo: string } | { ok: false; status: number; code: string; message: string }> {
+  const res = await request('POST', '/submit');
+  if (res.ok) {
+    const data = await res.json();
+    return { ok: true, redirectTo: data.redirectTo };
+  }
+  const err = await res.json().catch(() => ({}));
+  return { ok: false, status: res.status, code: err.code ?? '', message: err.message ?? `Submit failed (${res.status})` };
+}
+
+async function skipMfaBinding(): Promise<void> {
+  await request('POST', '/profile/mfa/mfa-skipped');
+}
+
 export async function signIn(identifier: string, password: string): Promise<string> {
   await initInteraction();
   const verificationId = await verifyPassword(identifier, password);
   await identifyUser(verificationId);
-  const res = await request('POST', '/submit');
-  if (!res.ok) {
-    const err = await res.json().catch(() => ({}));
-    if (err.code === 'user.missing_mfa') {
-      throw new MfaRequiredError();
-    }
-    throw new Error(err.message || `Submit failed (${res.status})`);
+  const result = await trySubmit();
+  if (result.ok) return result.redirectTo;
+
+  // MFA already enrolled — user must verify (show TOTP input)
+  if (result.code === 'user.missing_mfa' || result.code === 'session.mfa.require_mfa_verification') {
+    throw new MfaRequiredError();
   }
-  const data = await res.json();
-  return data.redirectTo;
+
+  // MFA not enrolled, UserControlled policy — skip the binding prompt.
+  // Also fallback: any 422 with an MFA-related code we don't recognize — try skip before failing.
+  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);
 }
 
 // --- Registration ---