Fix high-dimensional ellipsoidal-ball volume overflow

[FlorianPfaff]

Summary

• compute the unit-ball volume prefactor in log space for dimensions above 4
• avoid premature gamma overflow (starting around 342 dimensions in float64)
• add an 80-digit mpmath regression check for both manifold volume and the uniform PDF

Bug

get_manifold_size() previously formed

pi**(d/2) / gamma(d/2 + 1)

before taking its logarithm. At d = 342, gamma(172) overflows to infinity although the true unit-ball volume is still representable (~8.30e-225). This made the reported volume zero and the uniform density at interior points infinite.

The fix evaluates the dimension-only prefactor directly in log space with lgamma, then combines it with the existing log-Cholesky determinant calculation.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Max errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no		no	7.4s
✅ JSON	prettier	7	0	0		0	0.61s
✅ JSON	v8r	7		0		0	5.6s
✅ MARKDOWN	markdownlint	68	0	0		0	2.38s
✅ MARKDOWN	markdown-table-formatter	68	0	0		0	0.57s
✅ PYTHON	black	2020	4	0		0	70.67s
✅ PYTHON	isort	2020	5	0		0	3.04s
✅ REPOSITORY	betterleaks	yes		no		no	1.39s
✅ REPOSITORY	checkov	yes		no		no	39.82s
✅ REPOSITORY	git_diff	yes		no		no	0.15s
✅ REPOSITORY	secretlint	yes		no		no	113.48s
✅ REPOSITORY	syft	yes		no		no	2.82s
✅ REPOSITORY	trivy-sbom	yes		no		no	3.08s
✅ YAML	prettier	11	0	0		0	0.73s
✅ YAML	v8r	11		0		0	16.69s
✅ YAML	yamllint	11		0		0	1.0s

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