fix: fix: install networkx in agents container for build-graph.py (#14)

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

docker/agents/Dockerfile

@@ -1,7 +1,8 @@
 FROM debian:bookworm-slim
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    bash curl git jq tmux cron python3 openssh-client ca-certificates \
+    bash curl git jq tmux cron python3 python3-pip openssh-client ca-certificates \
+    && pip3 install --break-system-packages networkx \
     && rm -rf /var/lib/apt/lists/*
 
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