fix(downloads): humanized reasons and TechInfo on the download panel (DL-2b)

- board organize hint uses DEAI-2 reasonLine; add transfer_failed, blocked,
  blocked_by_conflict, main_failed, not_imported_kind, target_root_not_managed,
  download_removed to the reason table with tests
- download detail / plans tab: internal ids, raw codes and JSON moved into TechInfo
- library versions tech block switched to TechInfo (TODO(DEAI-2))
- copy: glossary terms (no 接管/候选), plan reason codes no longer shown raw

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

apps/web/app/api/downloads.ts

@@ -179,7 +179,7 @@ export const DOWNLOAD_STATUS_TONE: Record<DownloadStatus, "success" | "warning"
 };
 
 export const PAUSE_REASON_LABEL = {
-  user: "用户暂停",
+  user: "手动暂停",
   threshold: "下载盘满暂停",
   policy: "策略暂停",
   agent: "智能体暂停",