Replace the per-body base curve with a scene-referred view transform

The base curve was a five-point spline on the unit square, flat past its
last point: every value above 1.0 left it as the same number, per
channel. Exposure and highlight recovery put values up there, and the
curve threw them away, then handed the result on as though it were
still scene-linear. The six per-body curves were also, by their own
file's account, hand-tuned shapes rather than measurements, and not
enough is known about where they came from to keep them (D19).

In their place, one view transform for every body (FR-DEV-3j): a
log-logistic sigmoid per channel, with the middle channel put back
between the other two so a hue survives the shoulder. Its two free
constants are solved from two conditions rather than set: scene grey
0.13, where the retired default curve put it, lands on display 0.18,
and the scene white four stops above grey lands on 1.0. So a highlight
a stop past sensor saturation still rolls into white, and the midtones
stay within 0.26 EV of the retired default between scene 0.03 and 1.0.
`dr_pipeline::view` holds the CPU reference and the WGSL, and the tests
there are FR-DEV-3j's acceptance criteria.

It is still fixed and still in the fused pass's tail, so a detail stage
still sees rendered values; the next commits make it an operation and
move it after the detail stage. It is skipped for a JPEG, as the base
curve was, and absent from the camera-space tap.

The base curve's database, its lookup and its twelve uniform slots go.
`RawImage` and `DemosaicedImage` lose the field, and the GPU test that
proved a curve reached the shader is replaced by one that renders the
view transform against the CPU reference and shows two highlights above
1.0 still render apart. The JPEG-and-sensor test now asserts the two
differ by exactly the view transform, where before an identity fixture
curve had made them match.

core/dr-decode/src/lib.rs

@@ -16,14 +16,12 @@
 //! second decoder can be put behind them without changing any of them
 //! (FR-RAW-2). [`Rawler`] is the one that ships; [`default`] hands it out.
 
-pub mod base_curve;
 mod decoder;
 mod error;
 mod locate;
 mod preview;
 pub mod profile;
 
-pub use base_curve::BaseCurve;
 pub use decoder::{default, Decoder, Rawler};
 pub use error::DecodeError;
 pub use locate::{
@@ -125,19 +123,6 @@ pub struct RawImage {
     /// for the light the frame was shot under; see [`profile::CameraProfile`].
     pub color_matrix: Option<[f32; 9]>,
     /// TRACES: FR-DEV-3e
-    /// The per-body rendering curve, the other half of the camera profile.
-    ///
-    /// The matrix above decides what the colours *are*; this decides what the
-    /// picture looks like. Carried on the decoded image rather than looked up
-    /// downstream because this is the only point in the system that knows
-    /// which body took the frame, and because it is not an edit: it belongs to
-    /// the file in the same way the masked-photosite crop does, and must never
-    /// reach a sidecar (FR-NC-9).
-    ///
-    /// [`BaseCurve::IDENTITY`] for an unknown body with no default in the
-    /// database, which renders exactly as this decoder did before profiles
-    /// existed.
-    pub base_curve: BaseCurve,
     /// The usable region of `data`, excluding masked and border photosites.
     pub crop: CropRect,
     /// TRACES: FR-MRG-3
@@ -592,15 +577,6 @@ fn decode_unguarded(bytes: &[u8]) -> Result<RawImage, DecodeError> {
         profile.as_ref().map(|p| p.xyz_to_cam()).as_ref(),
     );
 
-    // The rendering half of the profile (FR-DEV-3e). rawler's cleaned strings
-    // are preferred where it has them — they are what the shipped database is
-    // written against — and the matching folds the variants either way, so a
-    // DNG naming the same body differently still finds its curve.
-    let base_curve = base_curve::for_body(
-        image.camera.clean_make.as_str(),
-        image.camera.clean_model.as_str(),
-    );
-
     // TRACES: FR-MRG-3
     // A linear DNG — three samples per pixel, no colour filter array — is a
     // composite this application wrote (or any other demosaiced DNG). It
@@ -683,7 +659,6 @@ fn decode_unguarded(bytes: &[u8]) -> Result<RawImage, DecodeError> {
             .unwrap_or(u16::MAX),
         wb_coeffs,
         color_matrix,
-        base_curve,
         samples_per_pixel,
         profile,
         make: image.camera.clean_make.clone(),