Format the tree the way the gate asks for it

`cargo fmt --check` is a required step and had drifted across 45 files. Most of
it arrived this week: several operations were written in parallel worktrees and
merged by hand, and a hand-merge resolves conflicts without ever running the
formatter over the result.

No behaviour changes — this is `cargo fmt --all` and nothing else, kept as its
own commit so the next reader can skip it wholesale rather than search it for
one that matters.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

core/dr-gpu/src/mask.rs

@@ -582,10 +582,7 @@ impl MaskPass {
                 MaskSource::Subject { .. } => match subjects.filter(|s| slot < s.len()) {
                     Some(s) => (s, slot),
                     None => {
-                        log::warn!(
-                            "mask layer {} has no distance field; skipping",
-                            layer.id
-                        );
+                        log::warn!("mask layer {} has no distance field; skipping", layer.id);
                         continue;
                     }
                 },
@@ -599,7 +596,14 @@ impl MaskPass {
                 }
                 _ => {
                     let selected = self.selection_buffer(layer, field);
-                    self.draw(&mut encoder, slot as u32, &params, field, &selected, subject);
+                    self.draw(
+                        &mut encoder,
+                        slot as u32,
+                        &params,
+                        field,
+                        &selected,
+                        subject,
+                    );
                 }
             }
         }
@@ -730,14 +734,14 @@ impl MaskPass {
         // Still worth beginning the pass: the slice has to be cleared, or an
         // unpainted layer would show whatever the last edit left in it.
         let bind_group = (!batch.is_empty()).then(|| {
-            let params_buf = self
-                .ctx
-                .device
-                .create_buffer_init(&wgpu::util::BufferInitDescriptor {
-                    label: Some("mask-brush-params"),
-                    contents: bytemuck::bytes_of(params),
-                    usage: wgpu::BufferUsages::UNIFORM,
-                });
+            let params_buf =
+                self.ctx
+                    .device
+                    .create_buffer_init(&wgpu::util::BufferInitDescriptor {
+                        label: Some("mask-brush-params"),
+                        contents: bytemuck::bytes_of(params),
+                        usage: wgpu::BufferUsages::UNIFORM,
+                    });
             // Rebuilt per rasterisation rather than kept and patched. This runs
             // when a mask's shape changes, not per frame, and a few kilobytes
             // of stroke geometry is cheaper to upload than a residency scheme
@@ -901,12 +905,9 @@ impl MaskPass {
                     wgpu::BindGroupEntry {
                         binding: 3,
                         resource: wgpu::BindingResource::TextureView(
-                            subject
-                                .0
-                                .view(subject.1)
-                                .unwrap_or_else(|| {
-                                    self.empty_subject.view(0).expect("placeholder exists")
-                                }),
+                            subject.0.view(subject.1).unwrap_or_else(|| {
+                                self.empty_subject.view(0).expect("placeholder exists")
+                            }),
                         ),
                     },
                 ],
@@ -949,7 +950,11 @@ impl MaskPass {
     }
 
     fn ensure_array(&mut self, width: u32, height: u32, layers: u32) -> Result<(), GpuError> {
-        if self.array.as_ref().is_some_and(|a| a.matches(width, height, layers)) {
+        if self
+            .array
+            .as_ref()
+            .is_some_and(|a| a.matches(width, height, layers))
+        {
             return Ok(());
         }
 
@@ -1111,7 +1116,9 @@ mod tests {
         }));
 
         let mut pass = MaskPass::new(&ctx).expect("mask pass");
-        let array = pass.render(&stack, Some(&field), None, w, h).expect("render");
+        let array = pass
+            .render(&stack, Some(&field), None, w, h)
+            .expect("render");
         assert_eq!(array.size(), (w, h));
         assert_eq!(array.layers(), 1);
     }
@@ -1201,7 +1208,11 @@ mod tests {
         assert_eq!(batch.headers.len(), 1);
 
         let h = &batch.headers[0];
-        assert!(h.hi[0] - h.lo[0] > 0.2, "wide enough for the dab: {h:?}", h = (h.lo, h.hi));
+        assert!(
+            h.hi[0] - h.lo[0] > 0.2,
+            "wide enough for the dab: {h:?}",
+            h = (h.lo, h.hi)
+        );
         assert!(
             h.hi[1] - h.lo[1] > h.hi[0] - h.lo[0],
             "and taller than it is wide in normalised units, since the radius \