153k of 160k merge groups have only 1 control — no intra-group
dedup possible. Skip them in Phase 1, they become masters automatically.
Phase 2 (cross-group) still checks them via Qdrant embeddings.
Reduces Phase 1 from ~96h to ~2h.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>