Add Docker setup for untrusted PR review in isolated containers

Adds a dedicated Docker environment for reviewing untrusted pull requests
with codex/claude, keeping CLI auth state in volumes and using a separate
scratch workspace for PR checkouts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker/untrusted-review/Dockerfile

@@ -0,0 +1,44 @@
+FROM node:lts-trixie-slim
+
+RUN apt-get update \
+  && apt-get install -y --no-install-recommends \
+    bash \
+    ca-certificates \
+    curl \
+    fd-find \
+    gh \
+    git \
+    jq \
+    less \
+    openssh-client \
+    procps \
+    ripgrep \
+  && rm -rf /var/lib/apt/lists/*
+
+RUN ln -sf /usr/bin/fdfind /usr/local/bin/fd
+
+RUN corepack enable \
+  && npm install --global --omit=dev @anthropic-ai/claude-code@latest @openai/codex@latest
+
+RUN useradd --create-home --shell /bin/bash reviewer
+
+ENV HOME=/home/reviewer \
+  CODEX_HOME=/home/reviewer/.codex \
+  CLAUDE_HOME=/home/reviewer/.claude \
+  PAPERCLIP_HOME=/home/reviewer/.paperclip-review \
+  PNPM_HOME=/home/reviewer/.local/share/pnpm \
+  PATH=/home/reviewer/.local/share/pnpm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+
+WORKDIR /work
+
+COPY --chown=reviewer:reviewer docker/untrusted-review/bin/review-checkout-pr /usr/local/bin/review-checkout-pr
+
+RUN chmod +x /usr/local/bin/review-checkout-pr \
+  && mkdir -p /work \
+  && chown -R reviewer:reviewer /work
+
+USER reviewer
+
+EXPOSE 3100 5173
+
+CMD ["bash", "-l"]