fix(offline): cold-boot offline from the persisted session + profile

An installed PWA relaunched with the network off hung on the splash: C1's
precache served the shell, but bootstrap() adopted the session and fetched the
profile over the network, which hung. Persist the profile (on every online
adopt + refresh, cleared on logout) and short-circuit bootstrap when the
deliberate offline flag is sticky-on: with a cached session + profile, skip the
network and land straight in the offline lobby. Without a cached profile (never
online), drop the sticky flag and boot online — the first launch must be online.

- session.ts: saveProfile/loadProfile/clearProfile (mirror saveSession).
- offline.ts: shouldBootOffline decision (unit-tested).
- app.svelte.ts: persist in adoptSession + refreshProfile, clear on logout,
  the offline boot short-circuit in bootstrap.

Docs: ARCHITECTURE. Online cold-start unaffected (e2e 196); the offline boot is
contour-verified (the mock e2e cannot enter sticky-offline).

ui/src/lib/app.svelte.ts

@@ -43,6 +43,9 @@ import { parseStartParam } from './deeplink';
 import {
   clearOnboarding,
   clearSession,
+  clearProfile,
+  loadProfile,
+  saveProfile,
   loadOnboarding,
   loadPrefs,
   loadSession,
@@ -53,6 +56,8 @@ import {
 } from './session';
 import type { CoachSeries } from './coachmark';
 import { connection, reportOffline, reportOnline, resetConnection } from './connection.svelte';
+import { offlineMode, setOfflineMode } from './offline.svelte';
+import { shouldBootOffline } from './offline';
 import { isConnectionCode } from './retry';
 import { clearGameCache, getCachedGame, setCachedGame } from './gamecache';
 import { advanceCached } from './gamedelta';
@@ -460,6 +465,7 @@ export async function refreshProfile(): Promise<void> {
   if (!app.session) return;
   try {
     app.profile = await gateway.profileGet();
+    void saveProfile(app.profile); // keep the offline-boot cache fresh
   } catch {
     // Best-effort; the banner just stays as it was until the next fetch.
   }
@@ -517,6 +523,9 @@ async function adoptSession(s: Session): Promise<void> {
   await saveSession(s);
   try {
     app.profile = await gateway.profileGet();
+    // Persist the profile so a later offline cold start can launch from it (its variant
+    // preferences, dictionary versions and display name) without a network fetch.
+    void saveProfile(app.profile);
     // The live interface language follows the device — the explicit local choice (saved in
     // prefs) or the system guess made at bootstrap — and is no longer overridden from the
     // account here: the Telegram bot a user signs in through must not dictate the UI, so a
@@ -790,6 +799,24 @@ export async function bootstrap(): Promise<void> {
   // and skipped in the mock build; see lib/pwa.svelte.
   registerServiceWorker();
 
+  // Deliberate offline mode carried over from a prior session: with no network the session adoption
+  // + profile fetch below would hang the splash, so skip them and launch straight from the cached
+  // session + profile into the offline lobby. Without both (e.g. cleared storage, or an install that
+  // was never online), drop the sticky flag and fall through to the normal online flow — the first
+  // launch must be online.
+  if (offlineMode.active) {
+    const [offlineSession, offlineProfile] = await Promise.all([loadSession(), loadProfile()]);
+    if (shouldBootOffline({ offlineActive: true, hasSession: !!offlineSession, hasProfile: !!offlineProfile })) {
+      gateway.setToken(offlineSession!.token);
+      app.session = offlineSession!;
+      app.profile = offlineProfile!;
+      if (router.route.name === 'login' || router.route.name === 'confirm') navigate('/');
+      app.ready = true;
+      return;
+    }
+    setOfflineMode(false);
+  }
+
   const saved = await loadSession();
   // A VK ID web-link callback (?code&device_id&state) rides the URL after the redirect back
   // from VK; capture and clear it here (it needs the restored session to link against).
@@ -1023,6 +1050,7 @@ export async function logout(): Promise<void> {
   app.splashDone = false;
   gateway.setToken(null);
   await clearSession();
+  await clearProfile();
   app.session = null;
   app.profile = null;
   navigate('/login');

ui/src/lib/offline.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect, beforeEach } from 'vitest';
-import { loadOfflinePref, saveOfflinePref, offlineReady, missingDicts, offlinePreloadEligible } from './offline';
+import { loadOfflinePref, saveOfflinePref, offlineReady, missingDicts, offlinePreloadEligible, shouldBootOffline } from './offline';
 import type { Variant } from './model';
 
 // A minimal in-memory localStorage for the persistence tests (node has none).
@@ -45,4 +45,11 @@ describe('offline mode helpers', () => {
     expect(offlinePreloadEligible({ ...base, inVK: true })).toBe(false);
     expect(offlinePreloadEligible({ ...base, online: false })).toBe(false);
   });
+
+  it('shouldBootOffline requires the offline flag plus a cached session and profile', () => {
+    expect(shouldBootOffline({ offlineActive: true, hasSession: true, hasProfile: true })).toBe(true);
+    expect(shouldBootOffline({ offlineActive: false, hasSession: true, hasProfile: true })).toBe(false);
+    expect(shouldBootOffline({ offlineActive: true, hasSession: false, hasProfile: true })).toBe(false);
+    expect(shouldBootOffline({ offlineActive: true, hasSession: true, hasProfile: false })).toBe(false);
+  });
 });

ui/src/lib/offline.ts

@@ -58,3 +58,13 @@ export function offlinePreloadEligible(opts: {
 }): boolean {
   return opts.hasEmail && opts.standalone && !opts.inTelegram && !opts.inVK && opts.online;
 }
+
+/**
+ * shouldBootOffline decides whether a cold start skips the network and launches straight into
+ * offline mode: the deliberate offline flag is persisted-on AND a prior online session left a cached
+ * session and profile to start from. Without both (e.g. cleared storage, or a never-online install),
+ * the app must boot online once first — the caller then drops the sticky flag and continues online.
+ */
+export function shouldBootOffline(opts: { offlineActive: boolean; hasSession: boolean; hasProfile: boolean }): boolean {
+  return opts.offlineActive && opts.hasSession && opts.hasProfile;
+}

ui/src/lib/session.ts

@@ -3,7 +3,7 @@
 // re-login), with a localStorage fallback. Losing the store just means re-login —
 // acceptable, and for a guest it simply mints a fresh guest.
 
-import type { Session } from './model';
+import type { Session, Profile } from './model';
 import type { ThemePref } from './theme';
 import type { Locale } from './i18n/catalog';
 import type { BoardLabelMode } from './boardlabels';
@@ -119,6 +119,25 @@ export function clearSession(): Promise<void> {
   return kvDel(SESSION_KEY);
 }
 
+const PROFILE_KEY = 'profile';
+
+/** loadProfile reads the last persisted profile (or null). It backs the offline cold-boot: with no
+ *  network, bootstrap uses it instead of fetching a fresh one. */
+export function loadProfile(): Promise<Profile | null> {
+  return kvGet<Profile>(PROFILE_KEY);
+}
+
+/** saveProfile persists the caller's own profile so a later offline launch can start from it (its
+ *  variant preferences, dictionary versions and display name), best-effort. */
+export function saveProfile(p: Profile): Promise<void> {
+  return kvSet(PROFILE_KEY, p);
+}
+
+/** clearProfile drops the persisted profile (on logout, with the session). */
+export function clearProfile(): Promise<void> {
+  return kvDel(PROFILE_KEY);
+}
+
 export interface Prefs {
   theme: ThemePref;
   locale: Locale;