fix(offline): persist a plain profile snapshot; keep the sticky offline flag

The offline cold-boot never engaged: it persisted app.profile — a Svelte
$state proxy — which is not structured-cloneable, so the IndexedDB write threw
and fell back to a localStorage entry that loadProfile (IDB-only on a
successful-empty read) never reads. loadProfile returned null, the boot
short-circuit missed, and it even cleared the sticky offline flag — so offline
mode stopped persisting across relaunches (owner-observed on the contour).

- Persist $state.snapshot(app.profile) (a plain object) at both persist sites,
  so the IndexedDB write succeeds and loadProfile round-trips.
- Drop the setOfflineMode(false) fallback: keep the deliberate offline flag on a
  cache miss (the mode is the player's choice; an online boot re-persists the
  profile so the next launch goes offline). A truly offline launch with no
  cached profile is unreachable (enabling offline needs a prior online session).

ui/src/lib/app.svelte.ts

@@ -56,7 +56,7 @@ import {
 } from './session';
 import type { CoachSeries } from './coachmark';
 import { connection, reportOffline, reportOnline, resetConnection } from './connection.svelte';
-import { offlineMode, setOfflineMode } from './offline.svelte';
+import { offlineMode } from './offline.svelte';
 import { shouldBootOffline } from './offline';
 import { isConnectionCode } from './retry';
 import { clearGameCache, getCachedGame, setCachedGame } from './gamecache';
@@ -465,7 +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
+    void saveProfile($state.snapshot(app.profile)); // keep the offline-boot cache fresh (plain snapshot)
   } catch {
     // Best-effort; the banner just stays as it was until the next fetch.
   }
@@ -524,8 +524,10 @@ async function adoptSession(s: Session): Promise<void> {
   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);
+    // preferences, dictionary versions and display name) without a network fetch. Snapshot to a
+    // plain object first — the reactive $state proxy is not structured-cloneable, so it would fail
+    // the IndexedDB write and fall back to a localStorage entry that loadProfile never reads.
+    void saveProfile($state.snapshot(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
@@ -801,9 +803,10 @@ export async function bootstrap(): Promise<void> {
 
   // 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.
+  // session + profile into the offline lobby. Without a cached profile (e.g. storage cleared) fall
+  // through to the normal online flow but KEEP the sticky flag — the mode is the player's choice, and
+  // an online boot re-persists the profile so the next launch goes offline. (A truly offline launch
+  // with no cached profile is unreachable: enabling offline requires a prior online session.)
   if (offlineMode.active) {
     const [offlineSession, offlineProfile] = await Promise.all([loadSession(), loadProfile()]);
     if (shouldBootOffline({ offlineActive: true, hasSession: !!offlineSession, hasProfile: !!offlineProfile })) {
@@ -814,7 +817,6 @@ export async function bootstrap(): Promise<void> {
       app.ready = true;
       return;
     }
-    setOfflineMode(false);
   }
 
   const saved = await loadSession();