- chroma.py: remove detect_background_color — orphaned since auto-detection
goes through estimate_background_model -> _background_border_cluster;
nothing in the repo calls it.
- settings.py: fix stale "Segmentation always stays fp32" comment
(--precision now fans out to the BiRefNet models too).
- README: add a measured CPU performance section (9700X reference numbers,
memory ceiling explanation, Zen 2 fallback guidance).
- docs/hair_gap_artifacts.md: record that the cross-check cost note is
obsolete — reuse_as_seg returns the net model count to 2, bf16 and
chunked attention absorb the rest.
- docs/green_screen_matting_workflow.md: add the 2026-07 additions to the
architecture-evolution note.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
lhk229
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