feat(downloads): fold download plans into download panel (DL-3)

- Waiting plans (approval / disk space / automation off / queued) are
  active-segment rows on /download-tasks/board, merged by created_at,
  counted, with approve / cancel actions; ?plan= deep links and legacy
  /downloads/plans routes redirect to the panel
- Download detail shows "why this download" (source, purpose, replaced
  version, reasons); raw evaluation in tech info
- Failed / cancelled / expired plans appear in the entity download
  history; rejected / revoked / expired approvals close draft plans
- New GET /acquisition-plans/{id}/why, POST /acquisition-plans/{id}/cancel
- User-facing copy no longer says 下载计划; glossary updated

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/contracts/src/api.ts

@@ -1118,6 +1118,24 @@ export const Api = {
       body: execution.ManualAcquisitionRequest,
       response: execution.ManualAcquisitionResult,
     }),
+    why: ep({
+      method: "get",
+      path: "/acquisition-plans/{id}/why",
+      scope: "read",
+      summary:
+        "下载的来由：来源（订阅 / 智能体会话 / 手动）、目的（补缺 / 升级 / 换源）、被替换的版本、选中理由要点与原始评估",
+      params: IdParam,
+      response: board.DownloadWhy,
+    }),
+    cancel: ep({
+      method: "post",
+      path: "/acquisition-plans/{id}/cancel",
+      scope: "organize.execute",
+      summary:
+        "取消还没提交到下载器的计划（待批准 / 已预留）：释放收录版本与预算预留；已有下载任务的返回 409。待批准的计划请拒绝审批（拒绝后计划自动取消）",
+      params: IdParam,
+      response: execution.AcquisitionPlan,
+    }),
   },
   downloadTasks: {
     ...crud(
@@ -1138,7 +1156,7 @@ export const Api = {
       path: "/download-tasks/board",
       scope: "read",
       summary:
-        "下载面板：按进行中 / 已完成分组列出下载任务，附每个种子的实时速度、剩余时间、连接数与下载器总速度（实时数据短时缓存）",
+        "下载面板：按进行中 / 已完成分组列出下载任务（进行中含还没提交、在等批准或下载盘空间的计划，kind=plan），附每个种子的实时速度、剩余时间、连接数与下载器总速度（实时数据短时缓存）",
       query: board.DownloadBoardQuery,
       response: board.DownloadBoard,
     }),