Fix silent int overflow in Fraction.getFraction(double)

[alhudz]

Thanks for your contribution to Apache Commons! Your help is appreciated!

Before you push a pull request, review this list:

• Read the contribution guidelines for this project.
• Read the ASF Generative Tooling Guidance if you use Artificial Intelligence (AI).
• I used AI to create any part of, or all of, this pull request. Which AI tool was used to create this pull request, and to what extent did it contribute?
• Run a successful build using the default Maven goal with mvn; that's mvn on the command line by itself.
• Write unit tests that match behavioral changes, where the tests fail if the changes to the runtime are not applied. This may not always be possible, but it is a best practice.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Each commit in the pull request should have a meaningful subject line and body. Note that a maintainer may squash commits during the merge process.

---

Repro: Fraction.getFraction(2147483646.5) returns -3/2 and getFraction(1073741824.5) returns -2147483647/2.

Cause: the result numerator is rebuilt as numer0 + wholeNumber * denom0 in int. wholeNumber can be up to Integer.MAX_VALUE and denom0 is the convergent denominator (> 1 for any non-integer value), so the product overflows and wraps. The value is not representable as an int/int Fraction, so the documented ArithmeticException should be thrown instead of returning a wrong reduced fraction.

Fix: route the numerator reconstruction through the existing mulAndCheck and Math.addExact, so the overflow is rejected the same way the value > Integer.MAX_VALUE guard already rejects out-of-range input. Whole numbers (where denom0 == 1) and all in-range values are unaffected.

[garydgregory]

@alhudz

I checked the new assertions fail without the main changes and merged the PR 🚀

TY!