Fix fraction representation in output

Fix to_fraction() in src/pitch.py to handle negative exponents
correctly without floating point precision loss.

Before: 2573485501354569/2251799813685248
After:  8/7

src/pitch.py

@@ -42,11 +42,17 @@ class Pitch:
 
     def to_fraction(self) -> Fraction:
         """Convert to frequency ratio (e.g., 3/2)."""
-        from math import prod
+        from fractions import Fraction
 
-        return Fraction(
-            prod(pow(self.dims[d], self.hs_array[d]) for d in range(len(self.dims)))
-        )
+        numerator = 1
+        denominator = 1
+        for d in range(len(self.dims)):
+            exp = self.hs_array[d]
+            if exp >= 0:
+                numerator *= self.dims[d] ** exp
+            else:
+                denominator *= self.dims[d] ** (-exp)
+        return Fraction(numerator, denominator)
 
     def to_cents(self) -> float:
         """Convert to cents (relative to 1/1 = 0 cents)."""