`score_crop` returns only scores the gallery already accepted: the raw 0.55
line, or the fine-tuned head's own 0.40. The live path then ranked that
aggregate with `decide_identity(scale="cosine")`, whose defaults rewrite to
COSINE_ACCEPT 0.60 / COSINE_AMBIGUOUS 0.50 - a second, higher line. Every head
match between 0.40 and 0.60 was therefore refused or downgraded to ambiguous,
which is the live regression: the head's own training views score 0.57-0.77.
`engine.inspect` and `_classify_with_gallery` already avoid this by ranking
through `decision_for_match`, which applies only the published margin. The live
path now does the same: on the cosine scale it passes explicit zero accept
lines, so the margin gate is the only extra gate.
Regression tests: a 0.45 head-scale match is labelled (fails on the previous
code), and a 0.45/0.44 pair inside the margin stays unnamed.
Verified: `python -m unittest discover -s code -p 'test_*.py'` - 257 tests, OK,
2 skipped.
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