fix: correct fraction and truncate test expectations for negative zero and large values

- Update fraction.wren test to cover edge cases for negative zero, small fractions, and large mantissa approximations
- Fix truncate.wren expected output for negative zero cases from 0 to -0
- Add truncate tests for large 32-bit representation values with approximation notes

test/number/truncate.wren

@@ -1,8 +1,13 @@
 IO.print(123.truncate)      // expect: 123
 IO.print((-123).truncate)   // expect: -123
 IO.print(0.truncate)        // expect: 0
-IO.print((-0).truncate)     // expect: 0
+IO.print((-0).truncate)     // expect: -0
 IO.print(0.123.truncate)    // expect: 0
 IO.print(12.3.truncate)     // expect: 12
-IO.print((-0.123).truncate) // expect: 0
+IO.print((-0.123).truncate) // expect: -0
 IO.print((-12.3).truncate)  // expect: -12
+
+// Using 32-bit representation, values "beyond" those  two will lead to
+// approximation.
+IO.print((12345678901234.5).truncate)   // expect: 12345678901234
+IO.print((-12345678901234.5).truncate)  // expect: -12345678901234