Golden image Dockerfile + local build script

Debian bookworm with two clearly-labeled sections:
- ESSENTIAL: systemd, openssh-server, ca-certificates, curl, iproute2.
- OPINION: git, jq, ripgrep, fd, build-essential, shellcheck, mise,
  Docker CE (+ Compose v2 + buildx), tmux, htop, and friends.

Per-VM identity stripped at build time: /etc/machine-id cleared,
SSH host keys removed with a ssh.service drop-in that runs
`ssh-keygen -A` on first start so each VM gets a unique set.

The script is a parameterized wrapper around `docker build`; it also
supports `--push` to an OCI registry, which will be removed once the
bundle pipeline is in place.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

images/golden/Dockerfile

@@ -0,0 +1,88 @@
+# banger golden image — Debian bookworm sandbox for development + testing.
+#
+# Two sections:
+#   1. ESSENTIAL — what banger's lifecycle requires to boot the guest.
+#   2. OPINION   — developer conveniences curated for banger sandboxes.
+#
+# Banger's guest agents (vsock agent, network bootstrap, first-boot unit)
+# are injected at `banger image pull` time, not baked here. Keeping them
+# out means this image stays portable enough to run in other contexts.
+
+FROM debian:bookworm-slim
+
+ENV DEBIAN_FRONTEND=noninteractive \
+    LANG=C.UTF-8 \
+    LC_ALL=C.UTF-8
+
+# -------- 1. ESSENTIAL --------
+# Banger needs: an init (systemd), sshd (the only control channel),
+# TLS roots + curl (first-boot installs + mise installer), iproute2
+# (debugging; `ip` is still useful even when the kernel sets IP via cmdline).
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends \
+      systemd systemd-sysv \
+      openssh-server \
+      ca-certificates \
+      curl \
+      iproute2 \
+ && rm -rf /var/lib/apt/lists/*
+
+# -------- 2. OPINION --------
+# Developer sandbox conveniences. Language runtimes are deliberately
+# absent — `mise` (below) handles per-repo `.mise.toml`/`.tool-versions`
+# on first `vm run`.
+
+# Core CLI + search/nav + build toolchain + lint/debug + editor/session.
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends \
+      git jq less tree file unzip zip rsync \
+      ripgrep fd-find \
+      build-essential pkg-config make \
+      shellcheck sqlite3 \
+      iputils-ping dnsutils \
+      vim-tiny tmux htop \
+ && rm -rf /var/lib/apt/lists/*
+
+# Docker CE (with Compose v2 + buildx) from the official apt repo.
+# Nested-VM docker gives Compose workflows hostname/port isolation
+# per banger VM, which is a big part of the sandbox story.
+RUN install -m 0755 -d /etc/apt/keyrings \
+ && curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc \
+ && chmod a+r /etc/apt/keyrings/docker.asc \
+ && printf 'deb [arch=%s signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian bookworm stable\n' \
+      "$(dpkg --print-architecture)" > /etc/apt/sources.list.d/docker.list \
+ && apt-get update \
+ && apt-get install -y --no-install-recommends \
+      docker-ce docker-ce-cli containerd.io \
+      docker-buildx-plugin docker-compose-plugin \
+ && rm -rf /var/lib/apt/lists/*
+
+# mise — per-repo version manager. Installed system-wide so the
+# bashrc activation reaches every shell.
+RUN curl -fsSL https://mise.run | MISE_INSTALL_PATH=/usr/local/bin/mise sh \
+ && chmod 0755 /usr/local/bin/mise \
+ && install -d /etc/profile.d \
+ && printf '%s\n' 'if [ -x /usr/local/bin/mise ]; then eval "$(/usr/local/bin/mise activate bash)"; fi' \
+      > /etc/profile.d/mise.sh \
+ && chmod 0644 /etc/profile.d/mise.sh
+
+# Git default branch — matches the old customize.sh opinion.
+RUN git config --system init.defaultBranch main
+
+# `fd-find` installs as `fdfind` on Debian to avoid a long-standing name
+# clash. Expose the ergonomic name for interactive use.
+RUN ln -s /usr/bin/fdfind /usr/local/bin/fd
+
+# Strip per-image identity so every banger VM gets its own.
+#  - /etc/machine-id: systemd-firstboot regenerates at boot when empty.
+#  - SSH host keys: removed here; a ssh.service drop-in (below) runs
+#    `ssh-keygen -A` before sshd so the VM's first boot generates a
+#    unique set.
+RUN : > /etc/machine-id \
+ && rm -f /etc/ssh/ssh_host_*_key /etc/ssh/ssh_host_*_key.pub \
+ && install -d /etc/systemd/system/ssh.service.d \
+ && printf '[Service]\nExecStartPre=-/usr/bin/ssh-keygen -A\n' \
+      > /etc/systemd/system/ssh.service.d/regen-host-keys.conf
+
+# No CMD / ENTRYPOINT: banger boots this via systemd as PID 1 after
+# first-boot, not via `docker run`.