Add Docker-backed integration test rig

docker/test-agent/Dockerfile

@@ -0,0 +1,28 @@
+FROM rust:1.88.0-bookworm AS builder
+WORKDIR /build
+
+COPY Cargo.toml Cargo.lock ./
+COPY server/ ./server/
+COPY gigacode/ ./gigacode/
+COPY resources/agent-schemas/artifacts/ ./resources/agent-schemas/artifacts/
+COPY scripts/agent-configs/ ./scripts/agent-configs/
+
+ENV SANDBOX_AGENT_SKIP_INSPECTOR=1
+
+RUN --mount=type=cache,target=/usr/local/cargo/registry \
+    --mount=type=cache,target=/usr/local/cargo/git \
+    --mount=type=cache,target=/build/target \
+    cargo build -p sandbox-agent --release && \
+    cp target/release/sandbox-agent /sandbox-agent
+
+FROM node:22-bookworm-slim
+RUN apt-get update -qq && \
+    apt-get install -y -qq --no-install-recommends ca-certificates bash libstdc++6 > /dev/null 2>&1 && \
+    rm -rf /var/lib/apt/lists/*
+
+COPY --from=builder /sandbox-agent /usr/local/bin/sandbox-agent
+
+EXPOSE 3000
+
+ENTRYPOINT ["sandbox-agent"]
+CMD ["server", "--host", "0.0.0.0", "--port", "3000", "--no-token"]