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/e2e/telegram.spec.ts

@@ -35,6 +35,23 @@ test('Telegram launch auto-authenticates into the lobby and applies the theme',
     .toBe('#101418');
 });
 
+test('a Telegram launch fragment in the URL still lands on the lobby and normalises the hash', async ({
+  page,
+}) => {
+  await page.addInitScript((stub) => {
+    Object.assign(window, stub);
+  }, webAppStub());
+  // Telegram appends its launch params to the URL fragment on a cold launch; the router must
+  // not treat that as a route (it parsed as notfound, which re-keyed the pane and slid the
+  // lobby in as if returning from another screen).
+  await page.goto(
+    '/#tgWebAppData=query_id%3Dtest%26user%3D%257B%2522id%2522%253A1%257D&tgWebAppVersion=7.0&tgWebAppPlatform=ios',
+  );
+  await expect(page.getByText('Your turn')).toBeVisible();
+  // The lobby is the root: bootstrap normalised the launch-param fragment to '#/'.
+  await expect.poll(() => new URL(page.url()).hash).toBe('#/');
+});
+
 test('tg-fullscreen header keeps a constant native-nav gap as the font scales', async ({ page }) => {
   await page.goto('/');
   await page.getByRole('button', { name: /guest/i }).click();