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-gpu/src/demosaic.rs

@@ -10,7 +10,7 @@
 //! pass over this texture; it does not re-demosaic, which is what keeps the
 //! interaction budget (NFR-P9) reachable on a 24 MP file.
 
-use dr_decode::{BaseCurve, CfaPattern, RawImage};
+use dr_decode::{CfaPattern, RawImage};
 use wgpu::util::DeviceExt;
 
 use crate::{GpuContext, GpuError};
@@ -109,16 +109,6 @@ pub struct DemosaicedImage {
     color_matrix: [f32; 9],
     /// As-shot white balance, the neutral starting point for the WB control.
     as_shot_wb: [f32; 3],
-    /// TRACES: FR-DEV-3e
-    /// The camera profile's rendering curve, carried through for the adjust
-    /// pass exactly as `color_matrix` is.
-    ///
-    /// It rides on the image rather than on the edit graph because it is not
-    /// an edit: it belongs to the body that took the frame, the way the
-    /// masked-photosite crop and the EXIF orientation do, and a sidecar shared
-    /// between two bodies must never carry one body's rendering onto the
-    /// other's file (FR-NC-9).
-    base_curve: BaseCurve,
     /// Whether the texture holds gamma-encoded rather than linear values.
     non_linear: bool,
     /// Which upload this is, unique for the life of the process. See
@@ -165,15 +155,6 @@ impl DemosaicedImage {
         self.color_matrix
     }
 
-    /// TRACES: FR-DEV-3e
-    /// The camera profile's base curve, as five `(x, y)` points.
-    ///
-    /// [`BaseCurve::IDENTITY`] where the body is unprofiled or the source was
-    /// never raw, in which case the adjust pass skips the stage entirely.
-    pub fn base_curve(&self) -> BaseCurve {
-        self.base_curve
-    }
-
     /// As-shot white balance multipliers, green-normalised.
     ///
     /// The white balance control is expressed *relative* to these, so its
@@ -291,7 +272,6 @@ impl DemosaicedImage {
             // camera's base curve baked in by the camera; applying one again
             // would render the rendering, crushing the shadows and flattening
             // the highlights of an image that was already finished.
-            base_curve: BaseCurve::IDENTITY,
             non_linear: true,
             id: next_image_id(),
         })
@@ -368,7 +348,6 @@ impl DemosaicedImage {
             height,
             color_matrix: raw.color_matrix.unwrap_or(IDENTITY_3X3),
             as_shot_wb: [raw.wb_coeffs[0], raw.wb_coeffs[1], raw.wb_coeffs[2]],
-            base_curve: raw.base_curve,
             non_linear: false,
             id: next_image_id(),
         })
@@ -784,7 +763,6 @@ impl Demosaicer {
             // Whatever the profile database had for this body (FR-DEV-3e),
             // resolved at decode because that is the only place the make and
             // model are known.
-            base_curve: raw.base_curve,
             // Sensor data is linear by construction — the demosaic shader
             // normalises against black and white levels and applies no
             // transfer function.
@@ -1284,7 +1262,6 @@ mod tests {
             white_level: white,
             wb_coeffs: [1.0, 1.0, 1.0, 1.0],
             color_matrix: None,
-            base_curve: BaseCurve::IDENTITY,
             samples_per_pixel: 1,
             profile: None,
             make: String::new(),
@@ -1400,7 +1377,6 @@ mod tests {
             white_level: white,
             wb_coeffs: [1.0, 1.0, 1.0, 1.0],
             color_matrix: None,
-            base_curve: BaseCurve::IDENTITY,
             samples_per_pixel: 1,
             profile: None,
             make: String::new(),
@@ -1697,7 +1673,6 @@ mod tests {
             white_level: 16383,
             wb_coeffs: [1.0, 1.0, 1.0, 1.0],
             color_matrix: None,
-            base_curve: BaseCurve::IDENTITY,
             samples_per_pixel: 1,
             profile: None,
             make: String::new(),
@@ -1782,7 +1757,6 @@ mod tests {
                 1.0,
             ],
             color_matrix: None,
-            base_curve: BaseCurve::IDENTITY,
             samples_per_pixel: 1,
             profile: None,
             make: String::new(),