Minor from the final fix wave: _codes_for's "~20 min of SQL before any
model call" warning describes elements' per-code LLM classification
pass. lineage --all-payable also calls _codes_for but its own
--all-payable path (lineage_all) is one inverted pass over
fr_anchors — seconds, not minutes — so the warning there was
misleading. New warn_slow keyword (default True, elements' two call
sites unchanged; lineage --all-payable passes warn_slow=False).
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