Record the fresh sync receipt in the L1 cleanup summary card

Why: The merge gate requires a fresh authoritative-main sync recorded in the task card before merging into main.
Evidence: make evidence receipt appended; task-sync re-verified sync_base=aa9f98d (current main) changed=0 at 2026-10-20T11:53:24Z.
Impact: Task card bookkeeping only.
Refs: Dev PR #650

.task/final-cleanup-summary.md

@@ -91,3 +91,40 @@
 4. **L1 task card 已归档**（`.task/archive/feature-iam-role-permission-linked-capabilities.md`）
 
 按用户"继续"指令完成全部 4 项收尾。
+
+## 证据（Evidence）
+
+<!-- Local receipt: SELF. Digests detect corruption; they do not authenticate a reviewer or CI. -->
+```json
+{
+  "summary_schema": 1,
+  "source": "SELF",
+  "timestamp": "2026-10-20T11:52:35.549769+00:00",
+  "command": "make task-sync",
+  "exit_code": 0,
+  "cwd": "/tmp/wt-l1cleanup",
+  "before_head": "7755d6497947240156bbc546e5f213de69619ff1",
+  "after_head": "7755d6497947240156bbc546e5f213de69619ff1",
+  "branch": "feature/l1-final-cleanup-summary",
+  "target_branch": "main",
+  "target_head": "aa9f98d2e5b8ce36724f881752b0a95a353df987",
+  "root_target": "main",
+  "immediate_target": "main",
+  "before_tracked_diff_sha256": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+  "after_tracked_diff_sha256": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+  "output_tail": [
+    "make[1]: Entering directory '/tmp/wt-l1cleanup'",
+    "[worktree] before-sync: recursive component checks passed",
+    "[worktree] before-update: recursive component checks passed",
+    "[worktree] materialize: recursive component checks passed",
+    "[worktree] after-sync: recursive component checks passed",
+    "[evidence] WARN JSON receipt line 31: unverified: Expecting property name enclosed in double quotes: line 2 column 23 (char 26) ——关键检查须重跑并以 make evidence 重新写入",
+    "[synced] sync_base=aa9f98d2e5b8ce36724f881752b0a95a353df987 tested_head=7755d6497947240156bbc546e5f213de69619ff1 checked_at=2026-10-20T11:53:24Z changed=0 sync_target=main",
+    "[next] 跑正式验收（make test 等），证据写入任务卡",
+    "make[1]: Leaving directory '/tmp/wt-l1cleanup'"
+  ],
+  "output_sha256": "4794de8354e0d08d318e2fe346bbb52c4f8bdc2656648d3f983264852fe1be16",
+  "receipt_sha256": "a52668c28d07c7e3b2f43a7730937a9a55172fcca7678ae361e919df197daab4",
+  "receipt_path": "/home/weichen/.cache/agent-system-dev/evidence/a52668c28d07c7e3b2f43a7730937a9a55172fcca7678ae361e919df197daab4.json"
+}
+```