实现 Pingora 发行网关路由并关闭两处路由漂移待办

- 新增 RouteDecision::ReleaseGateway：/games/game_<32 位小写十六进制 id>/… 重写上游路径到 /api/game-distribution/releases/<gameId><asset>、清空 Cookie、不进 SPA fallback、不套接流保护分组、不受维护闸拦截，与 nginx 同名 location 同口径（只认小写 32 位十六进制）
- 路由矩阵新增 games_release_gateway 用例（含 upstreamPath 期望值）与对应断言；parity 门禁支持 release_gateway 并把 games_spa_fallback、games_release_gateway 列入必查清单
- check:pingora-gateway-smoke 新增三条运行时断言：重写到发行网关且上游拿不到 Cookie、/games/detail 仍走 SPA、/games/game/index.html 仍是真实 404
- 文档：Pingora 试点文档补「平台同源发行入口」语义；pitfalls 记录 SPA allowlist 三处真相源与「发行入口不是 SPA」；按 docs/project-memory/README.md 删除两份已关闭待办，关闭记录写入开放事项索引第五节
- 验证：网关 39 passed、check:pingora-route-parity OK（23 路由）、check:nginx-spa-routes OK（12 路由 / 3 模板）、check:pingora-gateway-smoke 通过、cargo fmt --all --check、check:production-ops、encoding / doc-index / diff 检查全绿；变异验证：矩阵 upstreamPath 写错或拿掉 /games/detail 都会立刻变红

deploy/pingora/nginx-route-parity.matrix.json

@@ -317,6 +317,27 @@
       },
       "docs": ["主站 SPA allowlist", "游戏目录 / 详情 / 游玩 / 我的 / 发布深链"]
     },
+    {
+      "id": "games_release_gateway",
+      "samplePath": "/games/game_0123456789abcdef0123456789abcdef/index.html",
+      "expect": {
+        "kind": "release_gateway",
+        "upstreamPath": "/api/game-distribution/releases/game_0123456789abcdef0123456789abcdef/index.html"
+      },
+      "nginx": {
+        "production": [
+          "location ~ \"^/games/(?<game_id>game_[0-9a-f]{32})(?<game_path>/.*)?$\"",
+          "proxy_set_header Cookie \"\";",
+          "proxy_pass http://genarrative_api/api/game-distribution/releases/$game_id$game_path;"
+        ],
+        "development": [
+          "location ~ \"^/games/(?<game_id>game_[0-9a-f]{32})(?<game_path>/.*)?$\"",
+          "proxy_set_header Cookie \"\";",
+          "proxy_pass http://genarrative_api/api/game-distribution/releases/$game_id$game_path;"
+        ]
+      },
+      "docs": ["/games/game_<32 位十六进制 id>/…", "平台同源发行入口"]
+    },
     {
       "id": "web_spa_case_trailing_slash",
       "samplePath": "/PROJECT/",