feat(ui): one-tap confirm deeplink screen + client language

Add the /confirm/<token> SPA route and Confirm screen: a prefetch-safe button
POSTs the token via a new confirmEmailLink RPC (client/transport/mock/codec +
ConfirmLinkResult model). A login adopts the minted session and enters the app; a
link shows confirmed / merge-in-the-app; an invalid or expired token asks for a new
code. Exempt /confirm from the no-session /login redirect. Forward the client
locale on the email request (authEmailRequest gains language → app.locale) so a
fresh web login email is localised. Handle the new 'profile' live-event sub-kind by
re-fetching the profile, so a link confirmed in another browser reflects in-app at
once. i18n en+ru.

ui/src/App.svelte

@@ -15,6 +15,7 @@
   import NewGame from './screens/NewGame.svelte';
   import SettingsHub from './screens/SettingsHub.svelte';
   import Stats from './screens/Stats.svelte';
+  import Confirm from './screens/Confirm.svelte';
   import Game from './game/Game.svelte';
   import CommsHub from './game/CommsHub.svelte';
   import Feedback from './screens/Feedback.svelte';
@@ -110,6 +111,8 @@
           <Feedback />
         {:else if router.route.name === 'stats'}
           <Stats />
+        {:else if router.route.name === 'confirm'}
+          <Confirm token={router.route.params.token} />
         {:else}
           <Lobby />
         {/if}

ui/src/lib/app.svelte.ts

@@ -409,6 +409,11 @@ function openStream(): void {
         if (e.sub === 'banner') {
           void refreshProfile();
         }
+        // The viewer's own profile changed out of band (an email confirmed via the
+        // one-tap deeplink opened in another browser): re-fetch it.
+        if (e.sub === 'profile') {
+          void refreshProfile();
+        }
         void refreshNotifications();
       }
     },
@@ -738,7 +743,7 @@ export async function bootstrap(): Promise<void> {
   if (saved) {
     await adoptSession(saved);
     if (router.route.name === 'login') navigate('/');
-  } else if (router.route.name !== 'login') {
+  } else if (router.route.name !== 'login' && router.route.name !== 'confirm') {
     navigate('/login');
   }
   app.ready = true;
@@ -915,7 +920,7 @@ export async function loginGuest(): Promise<void> {
 
 export async function requestEmailCode(email: string): Promise<boolean> {
   try {
-    await gateway.authEmailRequest(email);
+    await gateway.authEmailRequest(email, app.locale);
     return true;
   } catch (err) {
     handleError(err);
@@ -933,6 +938,20 @@ export async function loginEmail(email: string, code: string): Promise<void> {
   }
 }
 
+// confirmDeeplink verifies a one-tap email deeplink token opened from a confirmation
+// email. A login adopts the minted session and enters the app; a link reports whether
+// it confirmed or needs the interactive merge. It throws on an invalid/expired token,
+// which the confirm screen surfaces. This browser need not be signed in.
+export async function confirmDeeplink(token: string): Promise<'login' | 'linked' | 'merge_required'> {
+  const r = await gateway.confirmEmailLink(token);
+  if (r.purpose === 'login' && r.session) {
+    await adoptSession(r.session);
+    navigate('/');
+    return 'login';
+  }
+  return r.status === 'merge_required' ? 'merge_required' : 'linked';
+}
+
 export async function logout(): Promise<void> {
   closeStream();
   resetConnection();

ui/src/lib/client.ts

@@ -20,6 +20,7 @@ import type {
   HintResult,
   Invitation,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveResult,
@@ -64,8 +65,11 @@ export interface GatewayClient {
    *  cosmetic seed for a brand-new account). */
   authVK(params: string, displayName: string): Promise<Session>;
   authGuest(locale?: string): Promise<Session>;
-  authEmailRequest(email: string): Promise<void>;
+  authEmailRequest(email: string, language: string): Promise<void>;
   authEmailLogin(email: string, code: string): Promise<Session>;
+  /** Confirm a one-tap email deeplink token: a login returns a session to adopt; a
+   *  link returns a status ('confirmed' | 'merge_required'). */
+  confirmEmailLink(token: string): Promise<ConfirmLinkResult>;
 
   // --- profile / lists ---
   profileGet(): Promise<Profile>;

ui/src/lib/codec.test.ts

@@ -117,7 +117,7 @@ describe('codec', () => {
     expect(guest.browserTz()).toBe('-05:30');
 
     const email = fb.EmailRequestRequest.getRootAsEmailRequestRequest(
-      new ByteBuffer(encodeEmailRequest('a@example.com', '+00:00')),
+      new ByteBuffer(encodeEmailRequest('a@example.com', '+00:00', 'en')),
     );
     expect(email.email()).toBe('a@example.com');
     expect(email.browserTz()).toBe('+00:00');

ui/src/lib/codec.ts

@@ -31,6 +31,7 @@ import type {
   Invitation,
   InvitationInvitee,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveRecord,
@@ -212,13 +213,15 @@ export function encodeGuestLogin(locale: string, browserTz: string): Uint8Array
   return finish(b, fb.GuestLoginRequest.endGuestLoginRequest(b));
 }
 
-export function encodeEmailRequest(email: string, browserTz: string): Uint8Array {
+export function encodeEmailRequest(email: string, browserTz: string, language: string): Uint8Array {
   const b = new Builder(128);
   const e = b.createString(email);
   const tz = b.createString(browserTz);
+  const l = b.createString(language);
   fb.EmailRequestRequest.startEmailRequestRequest(b);
   fb.EmailRequestRequest.addEmail(b, e);
   fb.EmailRequestRequest.addBrowserTz(b, tz);
+  fb.EmailRequestRequest.addLanguage(b, l);
   return finish(b, fb.EmailRequestRequest.endEmailRequestRequest(b));
 }
 
@@ -232,6 +235,14 @@ export function encodeEmailLogin(email: string, code: string): Uint8Array {
   return finish(b, fb.EmailLoginRequest.endEmailLoginRequest(b));
 }
 
+export function encodeEmailConfirmLink(token: string): Uint8Array {
+  const b = new Builder(128);
+  const t = b.createString(token);
+  fb.EmailConfirmLinkRequest.startEmailConfirmLinkRequest(b);
+  fb.EmailConfirmLinkRequest.addToken(b, t);
+  return finish(b, fb.EmailConfirmLinkRequest.endEmailConfirmLinkRequest(b));
+}
+
 // --- response decoders ---
 
 function s(v: string | null): string {
@@ -730,6 +741,16 @@ export function decodeLinkResult(buf: Uint8Array): LinkResult {
   };
 }
 
+export function decodeConfirmLinkResult(buf: Uint8Array): ConfirmLinkResult {
+  const r = fb.EmailConfirmLinkResult.getRootAsEmailConfirmLinkResult(new ByteBuffer(buf));
+  const sess = r.session();
+  return {
+    purpose: (s(r.purpose()) || 'link') as ConfirmLinkResult['purpose'],
+    status: (s(r.status()) || 'confirmed') as ConfirmLinkResult['status'],
+    session: sess ? sessionFromTable(sess) : null,
+  };
+}
+
 // --- social decoders ---
 
 function decodeAccountRef(r: fb.AccountRef): AccountRef {

ui/src/lib/i18n/en.ts

@@ -36,6 +36,12 @@ export const en = {
   'login.sendCode': 'Send code',
   'login.codePlaceholder': '6-digit code',
   'login.signIn': 'Sign in',
+  'confirm.prompt': 'Confirm your email to finish.',
+  'confirm.action': 'Confirm',
+  'confirm.linked': 'Email confirmed.',
+  'confirm.merge': 'Almost done — finish the merge in the app.',
+  'confirm.close': 'You can close this window and return to the game.',
+  'confirm.expired': 'This link is invalid or has expired. Request a new code.',
   'login.codeSent': 'We sent a code to {email}.',
 
   'lobby.activeGames': 'Active games',

ui/src/lib/i18n/ru.ts

@@ -37,6 +37,12 @@ export const ru: Record<MessageKey, string> = {
   'login.sendCode': 'Отправить код',
   'login.codePlaceholder': 'Код из 6 цифр',
   'login.signIn': 'Войти',
+  'confirm.prompt': 'Подтвердите почту, чтобы завершить.',
+  'confirm.action': 'Подтвердить',
+  'confirm.linked': 'Почта подтверждена.',
+  'confirm.merge': 'Почти готово — завершите объединение в приложении.',
+  'confirm.close': 'Можно закрыть это окно и вернуться в игру.',
+  'confirm.expired': 'Ссылка недействительна или истекла. Запросите новый код.',
   'login.codeSent': 'Мы отправили код на {email}.',
 
   'lobby.activeGames': 'Активные игры',

ui/src/lib/mock/client.ts

@@ -27,6 +27,7 @@ import type {
   HintResult,
   Invitation,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveResult,
@@ -149,7 +150,10 @@ export class MockGateway implements GatewayClient {
   async authGuest(): Promise<Session> {
     return { ...SESSION };
   }
-  async authEmailRequest(): Promise<void> {}
+  async authEmailRequest(_email: string, _language: string): Promise<void> {}
+  async confirmEmailLink(_token: string): Promise<ConfirmLinkResult> {
+    return { purpose: 'link', status: 'confirmed', session: null };
+  }
   async authEmailLogin(): Promise<Session> {
     return { ...SESSION, isGuest: false };
   }

ui/src/lib/model.ts

@@ -355,6 +355,15 @@ export interface LinkResult {
   session: Session | null;
 }
 
+// ConfirmLinkResult is the outcome of a one-tap deeplink confirmation. purpose is
+// 'login' (session carries the minted credential to sign in) or 'link' (status is
+// 'confirmed' or 'merge_required' — the app finishes any merge from its manual flow).
+export interface ConfirmLinkResult {
+  purpose: 'login' | 'link';
+  status: 'confirmed' | 'merge_required';
+  session: Session | null;
+}
+
 export interface MatchResult {
   matched: boolean;
   game?: GameView;

ui/src/lib/routeparse.ts

@@ -15,6 +15,7 @@ export type RouteName =
   | 'friends'
   | 'feedback'
   | 'stats'
+  | 'confirm'
   | 'notfound';
 
 export interface Route {
@@ -58,6 +59,11 @@ export function parse(hash: string): Route {
       return { name: 'feedback', params: {} };
     case 'stats':
       return { name: 'stats', params: {} };
+    case 'confirm':
+      // The one-tap email deeplink: /confirm/<token>. The token is the confirmation
+      // authorization; the screen POSTs it (prefetch-safe), so a mail scanner's GET
+      // does not consume it.
+      return { name: 'confirm', params: { token: seg[1] ?? '' } };
     default:
       return { name: 'notfound', params: {} };
   }

ui/src/lib/transport.ts

@@ -101,8 +101,11 @@ export function createTransport(baseUrl: string): GatewayClient {
     async authGuest(locale) {
       return codec.decodeSession(await exec('auth.guest', codec.encodeGuestLogin(locale ?? '', browserOffset())));
     },
-    async authEmailRequest(email) {
+    async authEmailRequest(email, language) {
-      await exec('auth.email.request', codec.encodeEmailRequest(email, browserOffset()));
+      await exec('auth.email.request', codec.encodeEmailRequest(email, browserOffset(), language));
+    },
+    async confirmEmailLink(token) {
+      return codec.decodeConfirmLinkResult(await exec('auth.email.confirm_link', codec.encodeEmailConfirmLink(token)));
     },
     async authEmailLogin(email, code) {
       return codec.decodeSession(await exec('auth.email.login', codec.encodeEmailLogin(email, code)));

ui/src/screens/Confirm.svelte

@@ -0,0 +1,95 @@
+<script lang="ts">
+  import { confirmDeeplink } from '../lib/app.svelte';
+  import { t } from '../lib/i18n/index.svelte';
+
+  let { token }: { token: string } = $props();
+  // idle → busy → (login navigates away) | linked | merge | error. The token is
+  // confirmed only on the button press (a POST), so a mail scanner prefetching the
+  // link (a GET on the SPA route) never consumes it.
+  let stage = $state<'idle' | 'busy' | 'linked' | 'merge' | 'error'>('idle');
+
+  async function confirm(): Promise<void> {
+    if (!token) {
+      stage = 'error';
+      return;
+    }
+    stage = 'busy';
+    try {
+      const r = await confirmDeeplink(token);
+      // A login has already navigated into the app; a link stays here with a result.
+      stage = r === 'merge_required' ? 'merge' : 'linked';
+    } catch {
+      stage = 'error';
+    }
+  }
+</script>
+
+<main class="confirm">
+  <div class="card">
+    <div class="brand">{t('app.title')}</div>
+    {#if stage === 'idle' || stage === 'busy'}
+      <p>{t('confirm.prompt')}</p>
+      <button class="primary" disabled={stage === 'busy'} onclick={confirm}>
+        {t('confirm.action')}
+      </button>
+    {:else if stage === 'linked'}
+      <p class="ok">{t('confirm.linked')}</p>
+      <p class="muted">{t('confirm.close')}</p>
+    {:else if stage === 'merge'}
+      <p class="ok">{t('confirm.merge')}</p>
+      <p class="muted">{t('confirm.close')}</p>
+    {:else}
+      <p class="err">{t('confirm.expired')}</p>
+    {/if}
+  </div>
+</main>
+
+<style>
+  .confirm {
+    height: 100%;
+    display: grid;
+    place-items: center;
+    padding: 16px;
+  }
+  .card {
+    width: min(94vw, 360px);
+    background: var(--surface);
+    border: 1px solid var(--border);
+    border-radius: var(--radius);
+    box-shadow: var(--shadow);
+    padding: 24px;
+    display: flex;
+    flex-direction: column;
+    gap: 12px;
+    text-align: center;
+  }
+  .brand {
+    font-weight: 700;
+    letter-spacing: 0.04em;
+    color: var(--accent);
+  }
+  p {
+    margin: 0;
+  }
+  .muted {
+    color: var(--text-muted);
+    font-size: 0.9rem;
+  }
+  .ok {
+    font-weight: 600;
+  }
+  .err {
+    color: var(--danger, #c0392b);
+  }
+  button {
+    padding: 12px;
+    border-radius: var(--radius-sm);
+    border: 1px solid var(--accent);
+    font-weight: 600;
+    background: var(--accent);
+    color: var(--accent-text);
+  }
+  button:disabled {
+    opacity: 0.5;
+  }
+</style>