fix: finish a webmail hand-off with a TOTP code instead of failing

src/screens/LoginScreen.tsx

@@ -140,12 +140,27 @@ export default function LoginScreen({ onLogin, isAddMode = false, onCancel }: Lo
         // that's a cancellation, not a failure, so leave them where they were.
         finishIfSignedIn(wasAuthenticated);
       } catch (err) {
+        // The webmail hands back the password even when the account needs a
+        // second factor; finish the sign-in here with a code instead of
+        // failing (the user already proved the password once).
+        const pending = useAuthStore.getState().pendingTotpLogin;
+        if (err instanceof Error && err.name === 'TotpRequiredError' && pending) {
+          setEmail(pending.username);
+          setPassword(pending.password);
+          setServerUrl(pending.serverUrl);
+          setTotpRequired(true);
+          setBusy(null);
+          setNotice(describeLoginError(err, { serverUrl: target }));
+          setHistory((prev) => [...prev, step]);
+          setStep('password');
+          return;
+        }
         setNotice(describeLoginError(err, { serverUrl: target }));
       } finally {
         setBusy(null);
       }
     },
-    [finishIfSignedIn, isAddMode, loginViaWebmail],
+    [finishIfSignedIn, isAddMode, loginViaWebmail, step],
   );
 
   const handleEmailContinue = React.useCallback(async () => {

src/stores/auth-store.ts

@@ -41,6 +41,12 @@ export interface AuthState {
   accountId: string | null;
   activeAccountId: string | null;
   client: typeof jmapClient | null;
+  /**
+   * Set when a password sign-in was refused with "MFA code required"; the
+   * login screen re-runs it with a code via `login(..., { totp })`. Cleared
+   * on the next successful sign-in.
+   */
+  pendingTotpLogin: { serverUrl: string; username: string; password: string } | null;
 
   login: (
     serverUrl: string,
@@ -232,6 +238,7 @@ export const useAuthStore = create<AuthState>((set, get) => ({
   accountId: null,
   activeAccountId: null,
   client: null,
+  pendingTotpLogin: null,
 
   login: async (serverUrl, username, password, opts) => {
     set({ isLoading: true, error: null });
@@ -270,8 +277,14 @@ export const useAuthStore = create<AuthState>((set, get) => ({
       useEmailStore.getState().setActiveAccount(accountId);
 
       applyConnectedState(set, session, serverUrl.replace(/\/+$/, ''), username, accountId);
+      set({ pendingTotpLogin: null });
       void syncAccountDisplayName(accountId);
     } catch (err) {
+      if (err instanceof Error && err.name === 'TotpRequiredError') {
+        // Keep what the user (or the webmail hand-off) supplied so the code
+        // step doesn't make them retype the password.
+        set({ pendingTotpLogin: { serverUrl: serverUrl.replace(/\/+$/, ''), username, password } });
+      }
       const message = err instanceof Error && err.name === 'TotpRequiredError'
         ? 'Two-factor code required'
         : err instanceof AuthenticationError