Rewrite fleet.py to use a GNN-based approach: nodes are src_ip with ML feature
vectors, edges connect IPs sharing (JA4, ASN) pairs, GraphSAGE (2 SAGEConv
layers, in→64→32) produces 32D embeddings clustered by HDBSCAN. PyG NeighborLoader
activates for >50k nodes. Update thesis docs (§5.2, §6.4, §2, §8) to reflect
GraphSAGE architecture and PyG scalability.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>