Develop a linear DNG from windows and reduced copies of it

DemosaicedImage::linear_rgb16_window uploads part of a linear DNG, or a
box-reduced copy of it, and says where it sits in the frame; size() now
reports the frame and texture_size() the texels, and the fused pass
writes the window into the shader's uniforms. EditGraph::source_region
finds the part of the source a view reads, and tiles::plan cuts a render
too large for one texture into halo-grown, grid-aligned tiles.

The GPU test renders frames a tile at a time from their own windows and
compares them with the whole: identical for point operations, within one
code value when straightened with clarity on.

core/dr-gpu/src/adjust.rs

@@ -1350,6 +1350,13 @@ impl AdjustPass {
         // runs. See `DemosaicedImage::is_non_linear`.
         let non_linear = if source.is_non_linear() { 1.0 } else { 0.0 };
         uniforms[12..16].copy_from_slice(&[wb[0], wb[1], wb[2], non_linear]);
+        // TRACES: FR-DSP-2 | NFR-RES-2
+        // Which part of the photograph the texture holds. The whole of it for
+        // every source that fits in one texture, which writes back exactly
+        // what the composer put there.
+        let w = dr_pipeline::SOURCE_WINDOW_UNIFORM_OFFSET;
+        uniforms[w..w + dr_pipeline::SOURCE_WINDOW_UNIFORM_FIELDS]
+            .copy_from_slice(&source.window_uniforms());
         uniforms
     }