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-pipeline/tests/attributes.rs

@@ -40,7 +40,10 @@ fn the_groups_are_derivable_from_the_chain() {
     present.sort();
     present.dedup();
 
-    assert!(present.contains(&Attribute::Tone), "the chain has tonal work");
+    assert!(
+        present.contains(&Attribute::Tone),
+        "the chain has tonal work"
+    );
     assert!(present.contains(&Attribute::Colour));
     assert!(
         present.contains(&Attribute::Geometry),