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。

yingce-agent/Dockerfile

@@ -0,0 +1,19 @@
+# syntax=docker/dockerfile:1.7
+
+FROM node:22.19-alpine
+
+RUN apk add --no-cache ca-certificates wget \
+    && addgroup -S app \
+    && adduser -S app -G app
+
+WORKDIR /app
+COPY backend/agent-runtime/pi/package.json backend/agent-runtime/pi/package-lock.json /app/agent-runtime/
+RUN npm ci --omit=dev --ignore-scripts --prefix /app/agent-runtime
+COPY backend/agent-runtime/pi/agent-runtime.mjs /app/agent-runtime/agent-runtime.mjs
+COPY yingce-agent/server.mjs /app/server.mjs
+
+ENV NODE_ENV=production
+USER app
+EXPOSE 8081
+HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 CMD wget -qO- http://127.0.0.1:8081/healthz >/dev/null || exit 1
+CMD ["node", "server.mjs"]