feat(ui): offline-first foundations — bundled dicts + local-guest identity

The additive groundwork for the native offline-first experience (ANDROID_PLAN.md §D).
Inert until the native cold-boot lands: on the web these paths never fire, so web / VK /
Telegram behaviour is unchanged.

- ui/scripts/bundle-dicts.mjs copies the scrabble-dictionary release DAWGs into
  dist/dict/<variant>@<version>.dawg for the native pipeline (run after `pnpm build`,
  before `cap sync`).
- The dict loader gains a bundled tier between the IndexedDB and network tiers, attempted
  only on a native channel (a packaged app serves ./dict/<key>.dawg from its assets).
  Native-gated rather than the plan's "404 on the web" because the relative path would
  otherwise hit the gateway's own session-gated /dict/ route.
- __DICT_VERSION__ Vite define (from VITE_DICT_VERSION, default "dev") + its ambient
  declaration; the offline vs_ai / hotseat creates in NewGame fall back to it when a
  device-local guest has no profile-advertised version.
- New lib/localguest.ts: a persisted device-local guest id (no DB row); the offline vs_ai
  human seat uses it (and the localized common.guest name) when there is no server session.

svelte-check clean, vitest green, native + web builds clean. The cold-boot rewrite,
reconciliation, the Profile soft-sign-in gating and the offline-first e2e follow.

ui/scripts/bundle-dicts.mjs

@@ -0,0 +1,42 @@
+// Copies the production dictionary DAWGs into the build's app assets so a native (offline-first)
+// install can obtain a dictionary with no network: the loader's bundled tier fetches
+// ./dict/<dictKey>.dawg, where dictKey is "<variant>@<version>" (see lib/dict/store.ts). Run only in
+// the native pipeline (after `pnpm build`, before `cap sync`); web builds skip it and stay slim.
+//
+// Source: DICT_DIR — the unpacked scrabble-dictionary release (scrabble-dawg-<DICT_VERSION>.tar.gz),
+// the SAME set the backend image and CI consume, NOT the solver's committed test fixtures. The bundled
+// version label comes from VITE_DICT_VERSION (default "dev") and MUST equal the client's __DICT_VERSION__
+// so the loader requests the exact (variant, version) the file is named for. OUT_DIR overrides the
+// output root (default `dist`) — the e2e build points it at dist-e2e.
+
+import { existsSync, mkdirSync, copyFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+const srcDir = process.env.DICT_DIR;
+if (!srcDir) {
+  console.error('bundle-dicts: DICT_DIR is required (the unpacked scrabble-dictionary release dir)');
+  process.exit(1);
+}
+const version = process.env.VITE_DICT_VERSION || 'dev';
+const outDir = join(process.env.OUT_DIR || 'dist', 'dict');
+
+// The app's Variant enum value -> the release dawg file name (matches e2e-dict.mjs and the movegen
+// parity mapping).
+const dawgFor = {
+  scrabble_en: 'en_sowpods',
+  scrabble_ru: 'ru_scrabble',
+  erudit_ru: 'ru_erudit',
+};
+
+mkdirSync(outDir, { recursive: true });
+let copied = 0;
+for (const [variant, file] of Object.entries(dawgFor)) {
+  const src = join(srcDir, `${file}.dawg`);
+  if (!existsSync(src)) {
+    console.warn(`bundle-dicts: missing ${src} — the bundled tier will 404 for ${variant} (set DICT_DIR)`);
+    continue;
+  }
+  copyFileSync(src, join(outDir, `${variant}@${version}.dawg`));
+  copied++;
+}
+console.log(`bundle-dicts: copied ${copied}/${Object.keys(dawgFor).length} dawgs -> ${outDir} (version ${version})`);