style: rustfmt the Phase 1 test additions

The per-file Phase 1 test commits were written without running rustfmt
as I went; this pass formats the new test code (long assert_eq! lines
wrapped, etc.). Formatting-only — no behavioural change.

src/algorithms/bayesian_opt.rs

@@ -644,7 +644,10 @@ mod tests {
         // k = exp(-0.5 * (1)^2) = exp(-0.5) ≈ 0.6065
         let got = rbf_kernel(&[0.0], &[1.0], &[1.0], 1.0);
         let expected = (-0.5_f64).exp();
-        assert!((got - expected).abs() < 1e-12, "got {got}, expected {expected}");
+        assert!(
+            (got - expected).abs() < 1e-12,
+            "got {got}, expected {expected}"
+        );
     }
 
     #[test]