fix(download): 已入库任务不被 qB 中间态改回（H2）

importing / imported 只由整理侧推进：checkingResumeData / queuedDL / checkingUP / moving 等中间态只更新原始字段，不改回 queued / downloading / completed，completed_at 不重写；这期间也不做无进展判定。

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

packages/mapping/test/enums.test.ts

@@ -57,6 +57,11 @@ describe("下载状态", () => {
       st("paused", "threshold"),
     );
     expect(M.mergeObservedDownloadState(st("imported"), "removed")).toEqual(st("removed"));
+    // 已进入整理侧:qB 重启 / 重新校验 / 移动的中间态不把状态改回下载阶段
+    for (const o of ["queued", "downloading", "paused_by_user", "error", "missing_files"] as const) {
+      expect(M.mergeObservedDownloadState(st("imported"), o), o).toEqual(st("imported"));
+      expect(M.mergeObservedDownloadState(st("importing"), o), o).toEqual(st("importing"));
+    }
   });
 });