The camera-space tap: OutputMode::CameraLinear, composed with no operations

compose_camera_linear composes the fused pass with an empty operation
list, the file's orientation as the baseline, a view rect for the tile,
and a store of rgba32float. On the GPU, render_camera_linear is the only
entry that accepts it: it fills the profile uniforms neutral — unit white
balance, identity matrix, curve off — so what lands in the texture is the
sensor's numbers after the lens warp and nothing else (FR-MRG-2). A third
bind-group layout carries the format, as the linear one does, and the
readback is generalised to any pixel width for the f32 copy.

Thirty-two bits because the composite is written back at the sensor's
scale: a 14-bit sensor has 16 384 steps to white and f16 keeps 2 048 of
them in the top octave.

core/dr-pipeline/src/graph.rs

@@ -849,6 +849,14 @@ impl EditGraph {
         )
     }
 
+    /// TRACES: FR-MRG-2
+    /// The camera-space tap for a merge: this edit's lens corrections and
+    /// nothing else of it, stored at full precision. See
+    /// [`crate::operation::compose_camera_linear`].
+    pub fn compose_camera_linear(&self, view: crate::framing::CropRect) -> ComposedShader {
+        crate::operation::compose_camera_linear(&self.warps, self.framing.baseline(), view)
+    }
+
     /// TRACES: FR-DEV-19c
     /// [`Self::compose_for`], with one layer's mask drawn over the picture.
     ///