Preserve finite values at large rounding precision

Found while testing crates/geom/src/transform.rs:59

Co-Authored-By: GPT-5.6-Luna <noreply@openai.com>
Co-Authored-By: GPT-6-Luna <noreply@openai.com>

crates/geom/src/tests.rs

@@ -163,6 +163,13 @@ fn set_rotation_keeps_center() {
     }
 }
 
+#[test]
+fn round_to_handles_large_precision_without_changing_finite_values() {
+    assert_eq!(round_to(1.25, 400), 1.25);
+    assert_eq!(round_to(-1.25, 400), -1.25);
+    assert_eq!(round_to(1.23456, 2), 1.23);
+}
+
 #[test]
 fn reverse_subpaths_preserves_open_and_closed() {
     let mut open = BezPath::new();

crates/geom/src/transform.rs

@@ -57,6 +57,9 @@ pub fn rotate_about(xf: Affine, pivot: Point, degrees: f64) -> Affine {
 /// Round a value to `digits` decimals for display (avoids `-0` and float noise).
 pub fn round_to(v: f64, digits: i32) -> f64 {
     let f = 10f64.powi(digits);
+    if v.is_finite() && !f.is_finite() {
+        return v;
+    }
     let r = (v * f).round() / f;
     if r == 0.0 { 0.0 } else { r }
 }