Parse("10", NumberStyles.HexNumber) silently returns 10 instead of 16 (or rejecting the style): AllowHexSpecifier and AllowBinarySpecifier are ignored #177

What's wrong

Parse(ReadOnlySpan<char>, NumberStyles, IFormatProvider?) (PreciseNumber/PreciseNumber.cs:1200-1307) and TryParse (~1369) never look at NumberStyles.AllowHexSpecifier or NumberStyles.AllowBinarySpecifier (neither name appears in the file). Input that happens to be all decimal digits is parsed as decimal, so a wrong value comes back with no error.

static T ParseG<T>(string s, NumberStyles st) where T : INumberBase<T>
    => T.Parse(s, st, CultureInfo.InvariantCulture);

ParseG<PreciseNumber>("10", NumberStyles.HexNumber);      // 10   — BigInteger/int give 16; decimal/double throw ArgumentException
ParseG<PreciseNumber>("1010", NumberStyles.BinaryNumber); // 1010 — int gives 10
PreciseNumber.TryParse("10", NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var r); // true, r = 10
ParseG<PreciseNumber>("A", NumberStyles.HexNumber);       // FormatException

Reproduced against the net10.0 build at 907bd2d.

Why it matters

Generic-math code (T.Parse(s, NumberStyles.HexNumber, ...) over INumberBase<T>) gets a silently wrong number for PreciseNumber where every BCL type either gives the right answer or refuses the style. This is a gap left by the #132 fix (styles are now validated, but these two flags fall through). It's distinct from #152, which is about valid inputs being rejected.

Suggested fix

Either:

• throw ArgumentException when either flag is set, matching decimal and double, or
• support them for integer input, matching BigInteger.

Acceptance: the calls above either return 16 / 10 or throw ArgumentException (for both Parse and TryParse); add tests alongside the existing NumberStyles tests.