feat: add math/base/special/asechf

[Amansingh0807]

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Resolves a part of #649

Description

What is the purpose of this pull request?

This pull request:

• adds a C implementation for @stdlib/math/base/special/asechf.

The package computes the hyperbolic arcsecant of a single-precision floating-point number using the relationship:

$$asechf(x) = acosh(1/x)$$

Since acoshf does not yet have a C implementation, this implementation uses the double-precision acosh function with appropriate float conversions.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• ref [RFC]: Add C implementations to base special math functions (tracking issue) #649

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I used AI to generate the boilerplate code for the benchmark files and to generate the numerical test fixtures (input/output pairs) for test.c. The core implementation logic and mathematical correctness were manually verified against standard definitions.

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Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/asechf	$\color{red}157/160$ $\color{green}+0.00%$	$\color{green}4/4$ $\color{green}+0.00%$	$\color{red}1/2$ $\color{green}+0.00%$	$\color{red}157/160$ $\color{green}+0.00%$

The above coverage report was generated for the changes in this PR.

[Amansingh0807]

Hi @kgryte! I have implemented the C version of asechf (hyperbolic arcsecant for single-precision floats).

Implementation uses the formula: asechf(x) = acosh(1/x)

Since acoshf doesn't exist in stdlib yet, I'm using acosh (double-precision) with proper float conversions:

• C: (float)stdlib_base_acosh((double)(1.0f / x))
• JS: float64ToFloat32(acosh(1.0 / float64ToFloat32(x)))

This approach maintains accuracy while avoiding dependency on non-existent acoshf. The implementation can be optimized later when acoshf is added.

All tests passing, It follows stdlib conventions. Ready for review!

Ref: #649

[kgryte]

We need acoshf to be implemented before this PR can move forward; otherwise, we are just creating technical debt.

[kgryte]

Ref: #5812

[Amansingh0807]

Understood @kgryte. I agree that waiting for acoshf avoids future refactoring.

I will keep this PR open and monitor the progress of acoshf. Once that lands, I will update this implementation to use stdlib_base_acoshf directly and ping you for review.