服务器缓存按期限清理，审计快照默认不再落地

排盘缓存、官方快照、负缓存、网关任务和分盘段过期后会删掉。同一张盘的数字写法合成一把缓存键。失败快照只用短期限。自测留存、异步任务、增长合同、安全缓存和隐私标记；一万个文件的清理慢于 2 秒，命中率提升不到 2.5 倍，都按实测写入记录。

Co-Authored-By: Grok (agent loop)

scripts/vedastro_gateway.py

@@ -340,6 +340,30 @@ def probe_official_rest_health(*, force_refresh: bool = True) -> dict[str, Any]:
     return result
 
 
+def _gateway_snapshot_ttl_helpers():
+    try:
+        from vedastro_service_adapter import (
+            _official_full_snapshot_cache_ttl_seconds,
+            _official_full_snapshot_negative_ttl_seconds,
+        )
+    except ModuleNotFoundError:
+        from scripts.vedastro_service_adapter import (
+            _official_full_snapshot_cache_ttl_seconds,
+            _official_full_snapshot_negative_ttl_seconds,
+        )
+    return _official_full_snapshot_cache_ttl_seconds, _official_full_snapshot_negative_ttl_seconds
+
+
+def _gateway_official_snapshot_ttl_seconds() -> float:
+    positive, _negative = _gateway_snapshot_ttl_helpers()
+    return positive()
+
+
+def _gateway_official_snapshot_negative_ttl_seconds() -> float:
+    _positive, negative = _gateway_snapshot_ttl_helpers()
+    return negative()
+
+
 def gateway_status(*, force_refresh: bool = True) -> dict[str, Any]:
     from scripts.diagnose_vedastro_mode import build_report as build_vedastro_mode_report
 
@@ -368,7 +392,8 @@ def gateway_status(*, force_refresh: bool = True) -> dict[str, Any]:
         ),
         "sdk_version": _sdk_version(),
         "cache_ttl_seconds": config["cache_ttl_seconds"],
-        "official_full_snapshot_cache_ttl_seconds": _int_env("VEDASTRO_OFFICIAL_FULL_SNAPSHOT_CACHE_TTL_SECONDS", 0),
+        "official_full_snapshot_cache_ttl_seconds": _gateway_official_snapshot_ttl_seconds(),
+        "official_full_snapshot_negative_cache_ttl_seconds": _gateway_official_snapshot_negative_ttl_seconds(),
         "queue_enabled": config["queue_enabled"],
         "fail_open_local": config["fail_open_local"],
         "official_readiness": {