A linear DNG in and out: the writer, and a three-sample RawImage

dr-export gains write_linear_dng — LinearRaw, DNG 1.4, u16 samples at
the sensor's scale, the body's matrices with their illuminants, the
as-shot neutral, the EXIF block an export writes — streamed strip by
strip through a closure so the composite is never held (FR-MRG-11). The
tiff crate's directory is a map, so PhotometricInterpretation is written
over what new_image set, which is the trick the S15.1 spike thought it
had to hand-roll around. The test reads the file back through rawler.

dr-decode's RawImage carries samples_per_pixel (a linear DNG is 3), the
body's profile with its calibrations mapped back to EXIF illuminant
codes, and the cleaned make and model. The GPU uploads a three-sample
image as it is, normalised by black and white like a photosite, through
a full f16 conversion — subnormals kept, because a 14-bit LSB sits at
f16's smallest normal and rounding it to zero would crush exactly the
shadows the file was written to keep.

Cargo.lock

@@ -1465,6 +1465,7 @@ dependencies = [
  "log",
  "png",
  "pollster",
+ "rawler",
  "thiserror 2.0.20",
  "tiff",
  "zune-jpeg 0.4.21",
@@ -1499,6 +1500,7 @@ dependencies = [
  "bytemuck",
  "dr-decode",
  "dr-film",
+ "dr-pano",
  "dr-pipeline",
  "dr-segment",
  "dr-types",
@@ -1674,6 +1676,7 @@ dependencies = [
  "dr-gpu",
  "dr-ingest",
  "dr-lens",
+ "dr-pano",
  "dr-pipeline",
  "dr-plat",
  "dr-preset-xmp",