Lightroom Classic reads `ToneCurvePV2012Red/Green/Blue` only together with
`ToneCurvePV2012`: a packet with a channel curve and no master curve leaves the
photo unchanged there (rendered on a chart: the channel curve alone has no
effect, with an identity master curve it applies). Imports now do the same.
The preset-packet test helper uses made-up as-shot values.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>