Canonicalized-To Unification overview

canonicalized_to edges need unification to compact the graph. Audit (2026-05-08): 21 canonicalized_to edges exist, all mapping vendor-specific hook-surface aliases to 7 canonical hook surfaces (pre-tool-use, post-tool-use, stop, subagent-stop, notification, user-prompt-submit, pre-compact). These are clean, intentional mappings — no merging or compaction needed.