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-segment/src/semantic.rs

@@ -357,7 +357,6 @@ impl SemanticModel {
             options,
         ))
     }
-
 }
 
 /// Turn one forward pass into instances in source-image space.
@@ -543,7 +542,11 @@ fn assemble_mask(
             let (gx1, gy1) = ((gx0 + 1).min(pw - 1), (gy0 + 1).min(ph - 1));
 
             let mut acc = 0.0;
-            for (k, &c) in coeffs.iter().enumerate().take(PROTOTYPES.min(protos.shape()[0])) {
+            for (k, &c) in coeffs
+                .iter()
+                .enumerate()
+                .take(PROTOTYPES.min(protos.shape()[0]))
+            {
                 if c == 0.0 {
                     continue;
                 }
@@ -643,7 +646,12 @@ mod tests {
 
     #[test]
     fn letterbox_round_trips_a_landscape_window() {
-        let window = Window { x: 0.0, y: 0.0, w: 1600.0, h: 1067.0 };
+        let window = Window {
+            x: 0.0,
+            y: 0.0,
+            w: 1600.0,
+            h: 1067.0,
+        };
         let lb = Letterbox::fit(window.w, window.h);
 
         // A source point maps into the input and back to where it started.