- `DevelopSettings.hdr`: enabled, headroom limit (`max_ev`) and SDR-rendition
offsets (brightness, contrast, highlights, shadows, whites, clarity), with
control specs (`hdr.maxEv`, `hdr.sdr*`) and copied with the Light group.
- `ToneMap::hdr` / `display_hdr`: the SDR curve through the midtones, with
highlights lifted up to `2^max_ev`; identical to the SDR tables at peak 1.
- `OutputDepth::F32Hdr`: unclamped linear output up to the peak. The finish
stage carries the peak through highlight desaturation, gamut mapping,
encoding, curves, grain and LUT profiles; with HDR off every branch is the
SDR code path, bit for bit.
- `settings_for`: every non-HDR render (CPU and GPU) uses the SDR rendition.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>