Replace the frozen scalar-sigma stills partiality with a physical, refined model.
Per crystal, refine an orientation tilt (dpsi_x, dpsi_y) against the running merge
and recompute each reflection's partiality analytically from the refined geometry
(angular Ewald-proximity model, sigma(d*) = gamma_e*d*), with the per-crystal scale
G profiled out by the existing robust IRLS - no re-integration. A soft Gaussian
prior on dpsi tames weak-data overfit while staying inert on strong data. The
merge <-> refine loop iterates a few times.
This is now the stills default via ScalingSettings::stills_partiality_refine (on).
A single opt-out flag `--simple-stills` reverts to treating every reflection as a
full (p=1, single pass). Retires the experimental `--still-partiality` flag. The
viewer gains a "Partiality post-refinement (stills)" checkbox in Scaling settings.
Validated (integrate-once / --scale): CC1/2 and R_meas both improve on three
monochromatic serial-stills datasets (+2.8 / -10, +5.6 / -3.4, +2.1 / -4);
neutral on a pink-beam DMM set (already-full reflections); R-free/R-work down vs
a fixed model; competitive with CrystFEL partialator on matched frames.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
