feat: enhance coding harness, model security and system features

scripts/sandbox/Dockerfile

@@ -0,0 +1,38 @@
+# syntax=docker/dockerfile:1.7
+# Both upstream stages are official images pinned to the linux/amd64 manifest digest observed
+# on 2026-08-30. The final scratch stage intentionally drops inherited image metadata such as
+# VOLUME, CMD, ENTRYPOINT, healthcheck and environment before adding a minimal allowlist.
+FROM node:24-bookworm@sha256:9137a20e25879e0b557227b57e3ee4e9af4bde29eb3db66134cd1723e84f830b AS node
+FROM maven:3.9.16-eclipse-temurin-21-noble@sha256:edf045813426842617b1667456ddec0026885146465e890b897655d877ba3386 AS assembly
+
+USER root
+COPY --from=node /usr/local/ /usr/local/
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends ca-certificates git python3 ripgrep \
+    && rm -rf /var/lib/apt/lists/* \
+    && rm -f /usr/local/bin/pnpm /usr/local/bin/pnpx \
+    && corepack enable pnpm \
+    && corepack prepare pnpm@10.14.0 --activate \
+    && groupadd --gid 65532 harness \
+    && useradd --uid 65532 --gid 65532 --no-create-home --home-dir /tmp \
+        --shell /usr/sbin/nologin harness \
+    && java -version \
+    && mvn -version \
+    && node --version \
+    && npm --version \
+    && pnpm --version \
+    && python3 --version \
+    && rg --version \
+    && git --version
+
+FROM scratch
+COPY --from=assembly / /
+ENV PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
+    JAVA_HOME=/opt/java/openjdk \
+    MAVEN_HOME=/usr/share/maven \
+    HOME=/tmp \
+    LANG=C.UTF-8
+USER 65532:65532
+WORKDIR /workspace
+ENTRYPOINT []
+CMD []