Tempo.TryParse("NaNbpm@1/4") throws instead of returning false, and zero/negative/infinite beats are accepted, so Seconds() returns Infinity or negative time #305

What's wrong

Semantics.Music/Tempo.cs has two validation gaps.

1. TryParse can throw.

   • double.TryParse(..., NumberStyles.Float, ...) accepts "NaN".
   • The guard at Tempo.cs:87-89 is only bpm <= 0.0, which is false for NaN, so the value reaches Create.
   • Create (Tempo.cs:37) does check IsNaN, and throws ArgumentOutOfRangeException.

   That breaks the Try-pattern contract: anyone parsing untrusted text gets an exception.

2. Values that make Seconds meaningless are accepted.

   • "Infinitybpm@1/4" parses.
   • Duration.TryParse accepts 0/4 and -1/4.
   • Neither Tempo.TryParse nor Tempo.Create(double, Duration) checks that the beat is positive.

   Seconds(Duration) divides by Beat.AsWholeNotes, so these values produce Infinity or negative time.

Reproduced

In a scratch net10.0 app:

Suggested fix / acceptance criteria

• Create throws ArgumentOutOfRangeException when beatsPerMinute is not finite (IsNaN || IsInfinity on netstandard2.0) or when the beat's Numerator <= 0.
• TryParse returns false for the same inputs itself rather than relying on Create, so it never throws for any string.
• Tests: every row above returns false from TryParse, and Create throws for the invalid argument cases. "120bpm@1/4" still round-trips.