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]>

apps/server/src/modules/browser/routes.ts

@@ -262,7 +262,7 @@ export function registerBrowserRoutes(app: ModuleApp, svc: () => BrowserService)
           ...body.submit,
           sourceReleaseId: v.sourceReleaseId,
         });
-        if (!submission.submitted) note = "提交未生成下载计划，见 rejected";
+        if (!submission.submitted) note = "没有下载，原因见 rejected";
       } catch (e) {
         // 与 POST /acquisition-plans 相同的拒绝(未识别、无授权等):产物已暂存,结果照常返回
         if (!(e instanceof ApiException) || e.code === "internal") throw e;