修复在线游玩加载体验：加载期黑屏/空白与发行资源传输开销

- packages/shared 新增共享游戏加载面 PlatformGameLoadingSurface：封面/标题 + 动效进度 + 按时长推进的阶段文案（准备/资源/引擎）+ 慢加载提示，附用例
- 网页游玩页用共享加载面替换近黑壳上的一行小字，加载上限改为共享常量 PLATFORM_GAME_LOADING_TIMEOUT_MS
- 后台审核试玩补加载面、20 秒超时与「重新创建试玩会话」入口，新会话重置加载态；补两条用例
- 发行网关（api-server）对文本类发行资源按 Accept-Encoding 下发 gzip，并下发强 ETag、命中 If-None-Match 返回 304；补 5 条 Rust 用例
- E2E 脚本 check-game-distribution-ops-rollback-e2e 补压缩/Vary/ETag/304/不接受 gzip 四条断言
- 同步 pitfalls、开发运维文档、nginx README 与两份里程碑记录

src/components/game-distribution/GameDistributionPages.test.tsx

@@ -464,6 +464,28 @@ describe('GamePlayPage', () => {
     expect(recordGamePlayMock).toHaveBeenCalledWith('game-1');
   });
 
+  it('shows the shared loading surface until the release frame is ready', async () => {
+    render(<GamePlayPage gameId="game-1" onBack={vi.fn()} />);
+
+    await screen.findByRole('button', { name: /开始游戏/u });
+    fireEvent.click(screen.getByRole('button', { name: /开始游戏/u }));
+    const iframe = await screen.findByTitle('星轨防线 在线游玩');
+
+    // 发行包首屏要下完整个引擎：加载期必须有看得见的加载面，而不是一行小字或黑屏。
+    const loadingSurface = screen.getByRole('status');
+    expect(loadingSurface.textContent).toContain('星轨防线');
+    expect(
+      loadingSurface.classList.contains('platform-game-loading--player'),
+    ).toBe(true);
+    expect(
+      loadingSurface.querySelector('.platform-game-loading__track'),
+    ).not.toBeNull();
+
+    fireEvent.load(iframe);
+    expect(screen.queryByRole('status')).toBeNull();
+    expect(iframe.className.includes('game-player-frame--ready')).toBe(true);
+  });
+
   it('rejects an unsafe release entry URL before rendering an iframe', async () => {
     getGameMock.mockResolvedValueOnce(
       createGame({

src/components/game-distribution/GamePlayPage.tsx

@@ -1,5 +1,9 @@
 import './gameDistribution.css';
 
+import {
+  PLATFORM_GAME_LOADING_TIMEOUT_MS,
+  PlatformGameLoadingSurface,
+} from '@genarrative/shared/components';
 import {
   ArrowLeft,
   Expand,
@@ -26,8 +30,11 @@ import { GameCover } from './GameGalleryPage';
 
 type GamePlayPageProps = { gameId: string | null; onBack: () => void };
 
-/** 发行包首屏加载上限：超过后给出显式超时与重试，不用无限期“正在启动”。 */
-export const GAME_PLAY_STARTUP_TIMEOUT_MS = 20_000;
+/**
+ * 发行包首屏加载上限：超过后给出显式超时与重试，不用无限期等待。
+ * 与后台审核试玩共用同一口径（`PLATFORM_GAME_LOADING_TIMEOUT_MS`）。
+ */
+export const GAME_PLAY_STARTUP_TIMEOUT_MS = PLATFORM_GAME_LOADING_TIMEOUT_MS;
 
 type GameStartupState = 'idle' | 'loading' | 'ready' | 'timeout';
 
@@ -212,7 +219,12 @@ export function GamePlayPage({ gameId, onBack }: GamePlayPageProps) {
           </div>
         ) : null}
         {hasStarted && startupState === 'loading' ? (
-          <div className="game-player-loading">游戏正在启动…</div>
+          <PlatformGameLoadingSurface
+            key={`game-loading-${frameRunId}`}
+            tone="player"
+            title={game.title}
+            cover={<GameCover game={game} compact />}
+          />
         ) : null}
         {hasStarted && startupState === 'timeout' ? (
           <PlatformStatusMessage

src/components/game-distribution/gameDistribution.css

@@ -517,15 +517,6 @@
 .game-player-frame--ready {
   opacity: 1;
 }
-.game-player-loading {
-  position: absolute;
-  inset: 0;
-  display: grid;
-  place-items: center;
-  color: rgba(255, 241, 227, 0.75);
-  font-size: 0.88rem;
-  font-weight: 700;
-}
 .game-play-safety-note {
   margin: 0;
   color: var(--platform-text-soft);
@@ -645,7 +636,6 @@
     -webkit-box-orient: vertical;
     -webkit-line-clamp: 2;
   }
-  .game-player-loading,
   .game-player-timeout {
     font-size: 0.8rem;
   }