UI: fix the lobby slide on Telegram cold launch (correct the cause)

The first attempt (the App.svelte `started` gate) targeted the first pane mount,
but the slide is a second render. On a Telegram cold launch the URL fragment is
Telegram's #tgWebAppData=... launch params, which the router parsed as notfound;
bootstrap's navigate('/') then corrected it to the lobby asynchronously, re-keying
the route pane (notfound -> lobby) and sliding the lobby in as if returning from a
screen. A reload was static because the hash was already #/.

Treat a Telegram launch fragment as the lobby root in the router, so the route is
correct from the first pane (no re-key, no slide). Extract the pure hash->Route
parsing into routeparse.ts so it unit-tests without a DOM, and revert the gate
(the first pane never slid — local transitions skip the initial mount, as clean
browser launches showed).

Tests: routeparse unit tests (incl. the tgWebApp fragment); an e2e that launches
with the fragment in the URL and asserts the lobby plus the normalised #/ hash.

ui/src/lib/routeparse.ts

@@ -0,0 +1,61 @@
+// Pure hash-path -> Route parsing for the router. Kept dependency-free and free of any
+// reactive state so it unit-tests in the node environment; router.svelte.ts wraps it with
+// the reactive route rune and navigation.
+
+export type RouteName =
+  | 'login'
+  | 'lobby'
+  | 'new'
+  | 'game'
+  | 'gameChat'
+  | 'gameCheck'
+  | 'profile'
+  | 'settings'
+  | 'about'
+  | 'friends'
+  | 'stats'
+  | 'notfound';
+
+export interface Route {
+  name: RouteName;
+  params: Record<string, string>;
+}
+
+/**
+ * parse maps a location hash to a Route. An empty hash is the lobby root. A Telegram Mini
+ * App cold launch appends its launch params to the URL fragment (#tgWebAppData=...&
+ * tgWebAppVersion=...); those are launch metadata, not a route, so the fragment is treated
+ * as the lobby root. Otherwise it would parse as notfound, and bootstrap's navigate('/')
+ * would then re-key the route pane (notfound -> lobby), sliding the lobby in on launch as if
+ * returning from another screen.
+ */
+export function parse(hash: string): Route {
+  const raw = hash.replace(/^#/, '');
+  if (raw === '' || raw.startsWith('tgWebApp')) return { name: 'lobby', params: {} };
+  const path = raw.split('?')[0];
+  const seg = path.split('/').filter(Boolean);
+  if (seg.length === 0) return { name: 'lobby', params: {} };
+  switch (seg[0]) {
+    case 'login':
+      return { name: 'login', params: {} };
+    case 'new':
+      return { name: 'new', params: {} };
+    case 'game':
+      if (!seg[1]) return { name: 'notfound', params: {} };
+      if (seg[2] === 'chat') return { name: 'gameChat', params: { id: seg[1] } };
+      if (seg[2] === 'check') return { name: 'gameCheck', params: { id: seg[1] } };
+      return { name: 'game', params: { id: seg[1] } };
+    case 'profile':
+      return { name: 'profile', params: {} };
+    case 'settings':
+      return { name: 'settings', params: {} };
+    case 'about':
+      return { name: 'about', params: {} };
+    case 'friends':
+      return { name: 'friends', params: {} };
+    case 'stats':
+      return { name: 'stats', params: {} };
+    default:
+      return { name: 'notfound', params: {} };
+  }
+}