Lightroom Classic 15.6 imports an XMP packet's channel curves only when it holds
ToneCurvePV2012 and all three of ToneCurvePV2012Red/Green/Blue; any partial set
(master + one or two channels, channels without the master) imports without
channel curves. #416 read them whenever the master curve was present.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>