feat(crawler): read back pixelrag visual evidence

docs/guides/browse_sh_crawler_playbook.md

@@ -85,6 +85,7 @@ python scripts/ops/report_pixelrag_crawler_integration.py \
 ```text
 /api/ai-automation/pixelrag-crawler-integration?platform=momo
 /api/ai-automation/pixelrag-crawler-integration?platform=pchome&manifest_url=https://24h.pchome.com.tw/prod/TEST-000000001&crawler=PChomeCrawler.search_products&trigger_reason=parser_empty
+/api/ai-automation/pixelrag-visual-evidence-readback?platform=pchome&manifest_id=4a93e95e5afb414bc8c3
 ```
 
 視覺證據 capture worker：
@@ -115,6 +116,14 @@ python3 scripts/ops/capture_pixelrag_visual_evidence.py \
   --max-tiles 12
 ```
 
+capture 成功後，receipt 會落在：
+
+```text
+runtime_artifacts/pixelrag_visual_evidence/<platform>/<manifest_id>/capture_receipt.json
+```
+
+API readback 只讀 receipt 和檔案存在狀態，不重新抓外站、不寫資料庫。
+
 安全邊界：
 
 - read-only；不登入、不下單、不加入購物車、不寫第三方狀態。