`NormalizedParameter.Normalize` returns NaN, not a clamped 0..1 value, for a log-range value ≤ 0 or a zero-width linear range (`decimal` throws)

[matt-edmondson]

What's wrong

NormalizedParameter<T>.Normalize (Semantics.Quantities/AudioEngineering/NormalizedParameter.cs ~L150-166) computes shaped as either:

• Math.Log(v / lo) / Math.Log(hi / lo) for a logarithmic taper, or
• (v - lo) / (hi - lo) for a linear taper.

It then relies on Math.Clamp(shaped, 0, 1), and the XML doc says "results outside [0, 1] are clamped". But Math.Clamp(NaN, …) returns NaN, and T.CreateChecked(NaN) throws for decimal.

Linear(min, max) doesn't validate that min != max, so a zero-width linear range reaches the same NaN path.

Reproduction

NormalizedParameter<double>.Logarithmic(20, 20000).Normalize(-5)      -> NaN   (Normalize(0) gives 0)
NormalizedParameter<double>.Linear(1, 1).Normalize(1)                 -> NaN
NormalizedParameter<decimal>.Logarithmic(20m, 20000m).Normalize(-5m)  -> OverflowException

The type exists to give a plugin host a [0, 1] position, and NaN is exactly what an automation lane must not receive.

Suggested fix / acceptance criteria

• With a log taper, map a value where v / lo <= 0 to the nearer end (0).
• Map a NaN shaped to 0.
• For a degenerate range, either reject min == max in Linear/Skewed, or return 0.
• Add tests for the three cases above.

[matt-edmondson]

Triage

• Category: Bug
• Priority: Medium. The contract ("clamped to [0, 1]") is broken for out-of-domain input. The call returns NaN for double and throws for decimal, and NaN is exactly what a plugin automation lane must not receive. It only happens with out-of-range or degenerate input.
• Area / suggested assignment: Semantics.Quantities/AudioEngineering/NormalizedParameter.
• Duplicates: none found.
• In progress: no open PR.

Suggested next step: add a NaN guard before Math.Clamp, map v/lo <= 0 to 0, and reject min == max at construction. Rejecting it at construction is better than returning 0, because the misconfiguration then shows up where it is made.

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