Close 1 merged task card(s) and archive them

Why: branches merged into main had left their task cards open; backfill status and archive to prevent bookkeeping debt.
Evidence: feature-pin-backend-ext8b.md(PR#466) — merges verified via git log --merges against origin/main.
Impact: .task/*.md moved to .task/archive/ with status backfilled; no code or submodule change.
Refs: task.sh close (card-autoclose-r1)

.task/archive/feature-pin-backend-ext8b.md

@@ -1,6 +1,6 @@
 # feature/pin-backend-ext8b 任务卡
 
-任务主记录：<PR 链接，交付前填写>；状态：进行中；owner：weichen
+任务主记录：PR #466 https://git-home.u1680832.nyat.app:30319/weichen/Agent-System-Dev/pulls/466（merge f16a2f97f2）；状态：已完成（回填）；owner：weichen
 
 ## 基线与授权
 
@@ -68,7 +68,7 @@
 | 时间(UTC) | 命令 | 被测HEAD | exit | 来源 | sha256(16) |
 |---|---|---|---|---|---|
 
-## 结果与验证（完成后填写）
+## 结果与验证
 
 - 结果：
 - 验证：<结论摘要 PASS/FAIL/SKIP/NOT_RUN 逐项；逐条证据由 make evidence 写入上方证据表>
@@ -203,3 +203,9 @@
   "receipt_sha256": "9d4be39bf7df4299466777cac446c4d4c757c6339e12902bd3058f31604bc623"
 }
 ```
+
+## 闭合记录（card-autoclose 回填）
+
+- 依据：merge f16a2f97f2f4b49f7a977bbbce33547527263827（PR #466）已包含于 origin/main，分支成果已落盘；本段为合入后回填。
+- 合并主题：Merge pull request 'Pin backend to EXT-8b resource authorization contract' (#466) from feature/pin-backend-ext8b into main
+- 归档：随闭合移入 .task/archive/；任务执行期的过程证据见原任务记录与 PR。