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/web/app/lib/labels.ts

@@ -150,7 +150,7 @@ export const ACTOR_TYPES = [
 ];
 export const actorTypeLabel = (t: string) => ACTOR_TYPES.find((a) => a.value === t)?.label ?? t;
 
-/** 下载计划 statusReason(`added`、`organize:succeeded` 等)→ 中文;不认识的原样显示 */
+/** 计划 statusReason(`added`、`organize:succeeded` 等)→ 中文;不认识的原样显示 */
 const PLAN_REASON: Record<string, string> = {
   added: "已添加到下载器",
   "organize:succeeded": "整理成功",

apps/web/app/lib/reasons.ts

@@ -28,7 +28,7 @@ export function reasonCode(r: { code?: string | null; message?: string | null }
   return [c, m && looksLikeCode(m) && m !== c ? m : null].filter(Boolean).join(" · ") || null;
 }
 
-/** 原因串里的内部码替换成人话(如下载计划 statusReason、任务 waitReason) */
+/** 原因串里的内部码替换成人话(如计划 statusReason、任务 waitReason) */
 export function humanizeReason(v: string | null | undefined): string | null {
   if (!v) return null;
   return looksLikeCode(v) ? reasonLine(v, v) : v;