fix: add non-root user to claude-runner container

Claude Code CLI refuses --dangerously-skip-permissions when running
as root. Add a 'runner' user for headless container execution.

Author: mariuspruvot

infra/docker/claude-runner/Dockerfile

@@ -13,9 +13,12 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     npm install -g @anthropic-ai/claude-code && \
     apt-get clean && rm -rf /var/lib/apt/lists/*
 
+RUN useradd -m -s /bin/bash runner
+
 WORKDIR /workspace
 
 COPY entrypoint.sh /entrypoint.sh
-RUN chmod +x /entrypoint.sh
+RUN chmod +x /entrypoint.sh && chown runner:runner /workspace
 
+USER runner
 ENTRYPOINT ["/entrypoint.sh"]