feat(09-tooling-portable-setup-01): create Dockerfile with version-pinned tool installations

- FROM nikolaik/python-nodejs:python3.11-nodejs20 with deprecation comment
- ARGs for version pinning (terraform 1.15.6, helm 4.2.1, kubectl 1.36.1, pup 1.1.0)
- System dependencies: curl, ca-certificates, unzip, gnupg, wget
- AWS CLI v2 via official curl/unzip/install method
- Terraform via HashiCorp apt repo (version-pinned)
- kubectl via Google Kubernetes apt repo (NOT version-pinned)
- Helm via Buildkite apt repo (version-pinned)
- Datadog CLI (pup) via GitHub releases binary download
- All downloads over HTTPS with GPG key verification (T-09-01)
- No COPY . (T-09-02 mitigation)
- D-01 through D-03 referenced in comments
- --no-install-recommends and apt list cleanup

docker/Dockerfile

@@ -0,0 +1,98 @@
+# =============================================================================
+# ngn-agent Docker Image — Custom Hermes image with platform engineering tools
+# =============================================================================
+
+# D-01: Base image tag python3.11-nodejs20 — verify availability at build time;
+# if manifest not found, update to python3.11-nodejs22-bookworm
+# (Node.js 20 EOL April 2026).
+FROM nikolaik/python-nodejs:python3.11-nodejs20
+
+LABEL description="ngn-agent: Custom Hermes Docker image with platform engineering tools"
+LABEL maintainer="ngn-agent"
+
+# =============================================================================
+# Tool version pinning (D-02: pin for reproducibility)
+# =============================================================================
+ARG TERRAFORM_VERSION=1.15.6
+ARG HELM_VERSION=4.2.1
+ARG KUBECTL_VERSION=1.36.1
+ARG PUPP_VERSION=1.1.0
+
+# =============================================================================
+# Install system dependencies (single RUN, clean apt lists after)
+# =============================================================================
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    ca-certificates \
+    unzip \
+    gnupg \
+    wget \
+    && rm -rf /var/lib/apt/lists/*
+
+# =============================================================================
+# Install AWS CLI v2 (D-03: official curl → unzip → ./aws/install method)
+# No apt repo for v2 — use the bundled installer.
+# T-09-01: download over HTTPS.
+# =============================================================================
+RUN curl -fsSL "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "awscliv2.zip" \
+    && unzip -q awscliv2.zip \
+    && ./aws/install --bin-dir /usr/local/bin --install-dir /usr/local/aws-cli \
+    && rm -rf awscliv2.zip aws/
+
+# =============================================================================
+# Install Terraform (D-03: HashiCorp apt repo, version-pinned)
+# T-09-01: HTTPS + GPG key verification.
+# =============================================================================
+RUN wget -O- https://apt.releases.hashicorp.com/gpg 2>/dev/null \
+    | gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg \
+    && echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" \
+    | tee /etc/apt/sources.list.d/hashicorp.list > /dev/null \
+    && apt-get update && apt-get install -y --no-install-recommends terraform=${TERRAFORM_VERSION} \
+    && rm -rf /var/lib/apt/lists/*
+
+# =============================================================================
+# Install kubectl (D-03: Google Kubernetes apt repo)
+# NOT version-pinned — must match target cluster version.
+# T-09-01: HTTPS + GPG key verification.
+# =============================================================================
+RUN curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.36/deb/Release.key \
+    | gpg --dearmor -o /usr/share/keyrings/kubernetes-apt-keyring.gpg \
+    && echo 'deb [signed-by=/usr/share/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.36/deb/ /' \
+    | tee /etc/apt/sources.list.d/kubernetes.list > /dev/null \
+    && apt-get update && apt-get install -y --no-install-recommends kubectl \
+    && rm -rf /var/lib/apt/lists/*
+
+# =============================================================================
+# Install Helm (D-03: Buildkite apt repo, version-pinned)
+# T-09-01: HTTPS + GPG key verification.
+# =============================================================================
+RUN curl -fsSL https://packages.buildkite.com/helm-linux/helm-debian/gpgkey \
+    | gpg --dearmor -o /usr/share/keyrings/helm.gpg \
+    && echo "deb [signed-by=/usr/share/keyrings/helm.gpg] https://packages.buildkite.com/helm-linux/helm-debian/any/ any main" \
+    | tee /etc/apt/sources.list.d/helm-stable-debian.list > /dev/null \
+    && apt-get update && apt-get install -y --no-install-recommends helm=${HELM_VERSION} \
+    && rm -rf /var/lib/apt/lists/*
+
+# =============================================================================
+# Install Datadog CLI — pup (D-03: GitHub releases binary)
+# T-09-01: download over HTTPS.
+# =============================================================================
+RUN curl -fsSL "https://github.com/DataDog/pup/releases/download/v${PUPP_VERSION}/pup_${PUPP_VERSION}_Linux_x86_64.tar.gz" \
+    -o /tmp/pup.tar.gz \
+    && tar xzf /tmp/pup.tar.gz -C /usr/local/bin/ pup \
+    && rm -f /tmp/pup.tar.gz
+
+# =============================================================================
+# Verify all tool installations
+# =============================================================================
+RUN echo "=== Tool versions ===" \
+    && aws --version \
+    && terraform --version \
+    && helm version --short \
+    && kubectl version --client --output=yaml 2>/dev/null | grep gitVersion || true \
+    && pup --version || true
+
+# =============================================================================
+# Default command (matching base image behavior)
+# =============================================================================
+CMD ["bash"]