fix math/number inconsistency

[CodePsy-2001]

related issue: #338

Summary

Fix interpreter crashes when implementation-approximated math results become non-finite values such as Infinity or NaN.

The reported case was:

Math.pow.call(0, -0.1, -Number.MAX_VALUE);
Math.pow(2, Number.MAX_VALUE);
Math.exp(1000);
Math.expm1(1000);
Math.cosh(1000);
Math.sinh(1000);

This previously crashed because math.pow(...) could return Double.PositiveInfinity, which was then wrapped as Math(BigDecimal). BigDecimal cannot represent infinity.

Changes

• Preserve non-finite results from mathematical approximation paths.
• Convert extended mathematical infinities through [approx-number].
• Avoid wrapping non-finite Double results as Math.
• Add regression test.

EvalSmallTest passes with 109 tests.

Discussions

Changes to this PR could harm the intended code design of 'Interpreter.scala', which needs to be reviewed.