feat(deploy): 画布 Agent - 独立 yingce-agent 容器并修复运行中断

生产会话不再因 stdout 管道提前关闭被误判失败。设置 YINGCE_AGENT_URL 后只走独立容器，失败不回退到内嵌进程。

backend/agent-runtime/pi/package-lock.json

@@ -8,7 +8,8 @@
       "dependencies": {
         "@earendil-works/pi-ai": "0.87.1",
         "@earendil-works/pi-coding-agent": "0.87.1",
-        "typebox": "1.3.27"
+        "typebox": "1.3.27",
+        "undici": "7.28.0"
       },
       "engines": {
         "node": ">=22.19.0"
@@ -2965,6 +2966,15 @@
       "integrity": "sha512-zu+jc1pcy4UiNThxikUr36f0Rybk9PEeCg/NE6adeWr/SKsdNO4EzZHYRDlv2YCVAfj3Odq3dESSo/jNyoBXzA==",
       "license": "MIT"
     },
+    "node_modules/undici": {
+      "version": "7.28.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-7.28.0.tgz",
+      "integrity": "sha512-cRZYrTDwWznlnRiPjggAGxZXanty6M8RV1ff8Wm4LWXBp7/IG8v5DnOm74DtUBp9OONpK75YlPnIjQqX0dBDtA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=20.18.1"
+      }
+    },
     "node_modules/undici-types": {
       "version": "8.9.0",
       "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-8.9.0.tgz",