style(simulation): cargo fmt the extent-inversion tests

Hand-written test bodies in step_canvas.rs did not match rustfmt. Caught by
the pre-push gate, which is exactly its job — team-patterns.md's note that
fmt auto-fixes and clippy is a quick lead patch, rather than something agents
should pre-emptively duplicate.

No behaviour change.

Co-Authored-By: Claude <noreply@anthropic.com>

server/src/atlas/step_canvas.rs

@@ -1677,8 +1677,14 @@ mod tests {
             StepCanvasRung::Quarter.extent_m(),
             Some(scale::QUARTER_M as f64)
         );
-        assert_eq!(StepCanvasRung::Block.extent_m(), Some(scale::BLOCK_M as f64));
-        assert_eq!(StepCanvasRung::Chunk.extent_m(), Some(scale::CHUNK_M as f64));
+        assert_eq!(
+            StepCanvasRung::Block.extent_m(),
+            Some(scale::BLOCK_M as f64)
+        );
+        assert_eq!(
+            StepCanvasRung::Chunk.extent_m(),
+            Some(scale::CHUNK_M as f64)
+        );
         assert_eq!(StepCanvasRung::Global.extent_m(), None);
     }
 
@@ -1937,7 +1943,11 @@ mod tests {
             (u32::MAX, u32::MAX), // adversarial
         ] {
             let (w, h) = resolve_canvas_extent(StepCanvasRung::Global, req, 6371.0);
-            assert_eq!(w, h * 2, "request {req:?} produced a non-2:1 canvas {w}x{h}");
+            assert_eq!(
+                w,
+                h * 2,
+                "request {req:?} produced a non-2:1 canvas {w}x{h}"
+            );
             assert!(h >= 1, "request {req:?} collapsed the canvas to zero rows");
         }
     }
@@ -1947,8 +1957,14 @@ mod tests {
     #[test]
     fn global_rung_still_clamps_an_adversarial_extent() {
         let (w, h) = resolve_canvas_extent(StepCanvasRung::Global, (u32::MAX, u32::MAX), 6371.0);
-        assert!(w <= STEP_CANVAS_MAX_EXTENT_AXIS, "width {w} escaped the axis cap");
-        assert!(h <= STEP_CANVAS_MAX_EXTENT_AXIS, "height {h} escaped the axis cap");
+        assert!(
+            w <= STEP_CANVAS_MAX_EXTENT_AXIS,
+            "width {w} escaped the axis cap"
+        );
+        assert!(
+            h <= STEP_CANVAS_MAX_EXTENT_AXIS,
+            "height {h} escaped the axis cap"
+        );
     }
 
     /// A body with no radius is not a sphere (asteroid belt, oort cloud) and