Stop describing a base curve the pipeline no longer has

D19 retired the per-body base curve, moved the matrix ahead of the
edits and the film into the view transform's place, but a dozen doc
comments still listed the curve among what a pixel passes through, or
said the film skipped it. The detail stage's module doc still drew the
matrix after the edits and the last detail pass encoding, which the
view pass took over. The film crate's README gave the base curves as
its reason for being data, and the ops README's list of hand-written
nodes had neither the view transform nor three of the five kernels.

FR-MRG-2 gave the base curve as why the merge cuts below the profile;
the view transform is why now. The decision table still said colour
defaults were a per-body curve, and FR-DEV-3j said only the default
view transform skips a JPEG, where the node skips one whatever its
sliders say. frame-budget.md records the view pass as unmeasured.

docs/dev/panorama.md

@@ -143,7 +143,9 @@ composer already makes that a matter of uniforms rather than structure: the
 white balance, the matrix and the curve's active flag are all in the reserved
 uniform block, and a fused pass with no operations, `as_shot_wb = 1`,
 `cam_to_srgb = I` and `base_curve_last.z = 0` stores exactly camera-linear
-RGB after the warp. So the tap is:
+RGB after the warp. *(Since D19 there is no curve flag: the base curve is
+gone, and the tap composes no view transform, so the white balance and the
+matrix are the only uniforms it fills neutral.)* So the tap is:
 
 - `EditGraph::compose_camera_linear()` — the `LinearWorking` tail with an
   empty operation list and identity framing, paired by name with
@@ -158,8 +160,8 @@ be re-developed deserves the sensor's precision. The cost is 2× on buffers
 FR-MRG-11 already bounds.
 
 **What the DNG carries as a consequence:** the first source's `Make`,
-`Model` and `UniqueCameraModel` — so `base_curve::for_body` finds the 6D's
-curve (retired with the base curves, D19) — its `ColorMatrix1`/`2` with illuminants, and its `AsShotNeutral`. The
+`Model` and `UniqueCameraModel` — so `base_curve::for_body` found the 6D's
+curve, until D19 retired the per-body curves — its `ColorMatrix1`/`2` with illuminants, and its `AsShotNeutral`. The
 composite then develops through the same profile as its sources, applied
 once. The spike's 64 × 48 file (§8) already carries the matrix and neutral;
 the body name is a string.