feat(ui): lobby site-style sidebar + profile screen (#47)

- Wrap lobby and profile in a shared `lobby-shell.svelte` chrome:
  page-list sidebar (Overview/Profile) and a top "Player-xxxx"
  identity strip mirroring the project site's monospace look.
- Strip the legacy `lobby.title`, device-session-id `<code>`, and
  `lobby.greeting` paragraph; the identity strip both names the user
  and opens the profile editor.
- Add a top-level `profile` AppScreen with a three-field form
  (`display_name`, `preferred_language`, `time_zone`) backed by a new
  `src/api/account.ts` wrapper around `user.account.get`,
  `user.profile.update`, and `user.settings.update`. Saving switches
  the active i18n locale in-place when the new preferred language is
  one the UI ships translations for.
- Update e2e fixture + auth-flow / lobby-flow specs to use the new
  `lobby-account-name` testid and wait for the loaded identity before
  releasing pending `SubscribeEvents` (webkit revocation race). New
  `profile-screen.spec.ts` covers navigation, edit-save, and cancel.
- Sync `ui/docs/lobby.md` and `ui/docs/navigation.md` to the new
  layout.

Closes #47

ui/frontend/tests/e2e/auth-flow.spec.ts

@@ -159,9 +159,9 @@ async function completeLogin(page: Page): Promise<void> {
 	await page.getByTestId("login-code-input").click();
 	await page.getByTestId("login-code-input").fill("123456");
 	await page.getByTestId("login-code-submit").click();
-	// Sign-in switches the in-memory screen to the lobby; the device
-	// session id surfaces only on the lobby screen.
-	await expect(page.getByTestId("device-session-id")).toBeVisible();
+	// Sign-in switches the in-memory screen to the lobby; the identity
+	// strip rendered by `lobby-shell.svelte` is the lobby-loaded signal.
+	await expect(page.getByTestId("lobby-account-name")).toBeVisible();
 }
 
 test.describe("Phase 7 — auth flow", () => {
@@ -174,10 +174,7 @@ test.describe("Phase 7 — auth flow", () => {
 	}) => {
 		const mocks = await mockGatewayHappyPath(page, "Pilot");
 		await completeLogin(page);
-		await expect(page.getByTestId("device-session-id")).toHaveText(
-			"dev-test-1",
-		);
-		await expect(page.getByTestId("account-greeting")).toContainText("Pilot");
+		await expect(page.getByTestId("lobby-account-name")).toContainText("Pilot");
 
 		mocks.pendingSubscribes.forEach((resolve) => resolve());
 	});
@@ -187,13 +184,13 @@ test.describe("Phase 7 — auth flow", () => {
 	}) => {
 		const mocks = await mockGatewayHappyPath(page, "Pilot");
 		await completeLogin(page);
-		await expect(page.getByTestId("account-greeting")).toBeVisible();
+		await expect(page.getByTestId("lobby-account-name")).toBeVisible();
 
 		await page.reload();
 		// The restored session re-renders the lobby screen directly (no
 		// `/lobby` route to land on).
-		await expect(page.getByTestId("device-session-id")).toHaveText(
-			"dev-test-1",
+		await expect(page.getByTestId("lobby-account-name")).toContainText(
+			"Pilot",
 		);
 
 		mocks.pendingSubscribes.forEach((resolve) => resolve());
@@ -204,7 +201,15 @@ test.describe("Phase 7 — auth flow", () => {
 	}) => {
 		const mocks = await mockGatewayHappyPath(page, "Pilot");
 		await completeLogin(page);
-		await expect(page.getByTestId("account-greeting")).toBeVisible();
+		// `lobby-account-name` becomes visible on lobby mount with the
+		// "loading account…" placeholder before the gateway responds.
+		// Wait for the loaded name to settle so the event-stream effect
+		// has had a chance to issue its `SubscribeEvents` request — the
+		// release below targets that pending stream, and an empty
+		// `pendingSubscribes` list defeats the test.
+		await expect(page.getByTestId("lobby-account-name")).toContainText(
+			"Pilot",
+		);
 
 		// Fire all pending SubscribeEvents requests with an empty 200
 		// response. Connect-Web's server-streaming reader sees no frames