feat(db): 待处理新增「下载器连不上」「下载目录读不到容量」两类（迁移 0073）

decision.kind 增加 downloader_offline / cache_volume_unknown,契约、原因文案与界面标签同步;
volume_state_unknown 的原因文案改为「下载目录读不到容量」并指向路径映射与容器挂载。

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Cxwgnn2pbzQ7rXv3rq7fei

packages/contracts/src/agent.ts

@@ -149,6 +149,10 @@ export const DecisionKind = z.enum([
   "identity_unresolved",
   /** 资源已绑定作品但集数待确认(无法换算 / 映射规则失效):按作品 + 来源季 + 发布组合并,附建议规则 */
   "episode_mapping",
+  /** 下载器连续不可达超过一段时间(按实例去重,恢复后自动关闭) */
+  "downloader_offline",
+  /** 下载目录读不到容量(路径映射 / 挂载问题,按卷去重,恢复后自动关闭) */
+  "cache_volume_unknown",
 ]);
 export type DecisionKind = z.infer<typeof DecisionKind>;
 export const DecisionStatus = z.enum(["open", "investigating", "awaiting_user", "resolved", "dismissed", "expired"]);