phase 8: lobby UI + cross-stack lobby command catalog + TS FlatBuffers

- Extend pkg/model/lobby and pkg/schema/fbs/lobby.fbs with public-games
  list, my-applications/invites lists, game-create, application-submit,
  invite-redeem/decline. Mirror the matching transcoder pairs and Go
  fixture round-trip tests.
- Wire the seven new lobby message types through
  gateway/internal/backendclient/{routes,lobby_commands}.go with
  per-command REST helpers, JSON-tolerant decoding of backend wire
  shapes, and httptest-based unit coverage for success / 4xx / 5xx /
  503 across each command.
- Introduce TS-side FlatBuffers via the `flatbuffers` runtime dep, a
  `make fbs-ts` target driving flatc, and the generated bindings under
  ui/frontend/src/proto/galaxy/fbs. Phase 7's `user.account.get` decode
  now uses these bindings as well, closing the JSON.parse vs
  FlatBuffers gap that would have failed against a real local stack.
- Replace the placeholder lobby with five sections (my games, pending
  invitations, my applications, public games, create new game) and the
  /lobby/create form. Submit-application uses an inline race-name
  form on the public-game card; create-game keeps name / description /
  turn_schedule / enrollment_ends_at always visible and the rest under
  an Advanced toggle with TS-side defaults.
- Update lobby/+page.svelte to throw LobbyError on non-ok result codes;
  GalaxyClient.executeCommand now returns { resultCode, payloadBytes }.
- Vitest binding round-trips, lobby.ts wrapper unit tests, lobby-page
  + lobby-create component tests, Playwright lobby-flow.spec covering
  create / submit / accept across all four projects. Phase 7 e2e was
  migrated to the FlatBuffers fixtures and to click+fill against the
  Safari-autofill readonly inputs.
- Mark Phase 8 done in ui/PLAN.md, mirror the wire-format note into
  Phase 7, append the new lobby commands to gateway/README.md and
  docs/ARCHITECTURE.md, add ui/docs/lobby.md.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -16,6 +16,13 @@ import { fromJson, type JsonValue } from "@bufbuild/protobuf";
 import { expect, test, type Page } from "@playwright/test";
 import { ExecuteCommandRequestSchema } from "../../src/proto/galaxy/gateway/v1/edge_gateway_pb";
 import { forgeExecuteCommandResponseJson } from "./fixtures/sign-response";
+import {
+	buildAccountResponsePayload,
+	buildMyApplicationsListPayload,
+	buildMyGamesListPayload,
+	buildMyInvitesListPayload,
+	buildPublicGamesListPayload,
+} from "./fixtures/lobby-fbs";
 
 interface MockSetup {
 	pendingSubscribes: Array<() => void>;
@@ -58,19 +65,36 @@ async function mockGatewayHappyPath(
 				ExecuteCommandRequestSchema,
 				JSON.parse(reqText) as JsonValue,
 			);
-			const accountJson = JSON.stringify({
-				account: {
-					user_id: "user-1",
-					email: "pilot@example.com",
-					user_name: "player-test",
-					display_name: displayName,
-				},
-			});
+			let payload: Uint8Array;
+			switch (req.messageType) {
+				case "user.account.get":
+					payload = buildAccountResponsePayload({
+						userId: "user-1",
+						email: "pilot@example.com",
+						userName: "player-test",
+						displayName,
+					});
+					break;
+				case "lobby.my.games.list":
+					payload = buildMyGamesListPayload([]);
+					break;
+				case "lobby.public.games.list":
+					payload = buildPublicGamesListPayload([]);
+					break;
+				case "lobby.my.invites.list":
+					payload = buildMyInvitesListPayload([]);
+					break;
+				case "lobby.my.applications.list":
+					payload = buildMyApplicationsListPayload([]);
+					break;
+				default:
+					payload = new Uint8Array();
+			}
 			const responseJson = await forgeExecuteCommandResponseJson({
 				requestId: req.requestId,
 				timestampMs: BigInt(Date.now()),
 				resultCode: "ok",
-				payloadBytes: new TextEncoder().encode(accountJson),
+				payloadBytes: payload,
 			});
 			await route.fulfill({
 				status: 200,
@@ -122,9 +146,14 @@ async function mockGatewayHappyPath(
 async function completeLogin(page: Page): Promise<void> {
 	await page.goto("/");
 	await expect(page).toHaveURL(/\/login$/);
+	// Inputs render `readonly` initially as a Safari autofill-suppression
+	// workaround; the attribute drops on first focus. Click first so the
+	// onfocus handler runs before fill checks editability.
+	await page.getByTestId("login-email-input").click();
 	await page.getByTestId("login-email-input").fill("pilot@example.com");
 	await page.getByTestId("login-email-submit").click();
 	await expect(page.getByTestId("login-code-input")).toBeVisible();
+	await page.getByTestId("login-code-input").click();
 	await page.getByTestId("login-code-input").fill("123456");
 	await page.getByTestId("login-code-submit").click();
 	await expect(page).toHaveURL(/\/lobby$/);
@@ -213,6 +242,7 @@ test.describe("Phase 7 — auth flow", () => {
 			"отправить код",
 		);
 
+		await page.getByTestId("login-email-input").click();
 		await page.getByTestId("login-email-input").fill("pilot@example.com");
 		await page.getByTestId("login-email-submit").click();
 		await expect(page.getByTestId("login-code-input")).toBeVisible();