M11.4: the X-T20 corpus RAF is fitted since the away-from-edges retry; update the test and the doc that said it was rejected

Found running cargo xtask ci with the corpus on Windows. The two changes
landed on the same day: the Fujifilm test (#282) expected the compressed
X-T20 file to keep the neutral fallback because its fit failed the gates
on all pixels (held-out RMS 0.114 against 0.10). The retry away from
edges (#263, issue #232) fits it (0.056), so the fit is accepted at both
sizes. Expect true.

docs/camera-preview-colour.md

@@ -56,7 +56,7 @@ The additional supplied folder contains 748 RAFs. Profiles were fitted separatel
 
 For validation, every fifth usable photo of each model in sorted path order was withheld. Profiles trained on the remaining 160 X-H2S and 436 X-T4 photos were tested on 41 and 109 withheld photos. Mean CIE76 ΔE against the camera JPEG was 9.86 → 1.70 with per-file fitting → 1.62 with the pooled X-H2S profile, and 13.64 → 2.43 → 2.34 for X-T4. The profiles improved 108 of 150 files; the largest regression against per-file fitting was 0.60 ΔE, with no previously accepted fit rejected. These are withheld files from the same limited scene collection, not independent coverage of all subjects or illuminants.
 
-The three original dark X-H2S wrench files have too little colour variation to learn a matrix, but now use the known profile to fit tone: ΔE 8.74 → 2.25, all accepted. The four original X-T4 files and two public X-T4 files remain accepted with the final bundled profile; they regress slightly against their own per-file fits (six-file mean 4.72 → 4.94), while remaining much closer than the neutral fallback (13.47). One public X-T20 reference still fails the gates and keeps the fallback.
+The three original dark X-H2S wrench files have too little colour variation to learn a matrix, but now use the known profile to fit tone: ΔE 8.74 → 2.25, all accepted. The four original X-T4 files and two public X-T4 files remain accepted with the final bundled profile; they regress slightly against their own per-file fits (six-file mean 4.72 → 4.94), while remaining much closer than the neutral fallback (13.47). The public X-T20 reference fails the gates on all pixels (held-out RMS 0.114) and passes on the second attempt away from edges (0.056, from 0.185 uncorrected), so it is fitted too.
 
 RAF inputs also work with `lightcraft-cli calibrate`. Tests cover real X-Trans/16-bit Bayer fits, profile use on dull scenes, per-file fitting after profile rejection, monochrome rejection, resolution independence, header/decoded relative WB, old-catalog WB transitions and invalid RAF calibration inputs. A full-size 6240×4160 X-T4 JPEG export also succeeded.