Validate stickiness inputs for mode transition matrices

[FlorianPfaff]

Summary

Fix the public sticky_mode_transition_matrix input contract so malformed stickiness values fail deterministically instead of being silently coerced or leaking NumPy-specific exceptions.

Bug

The compatibility wrapper validates n_modes but previously passed stickiness through unchanged. Consequently:

• True / False were silently accepted as probabilities 1.0 / 0.0.
• strings, complex values, and non-scalar arrays could fail with incidental TypeError / ambiguous-truth-value errors from NumPy rather than the documented ValueError contract.

Fix

• Require stickiness to be a finite real scalar in [0, 1].
• Explicitly reject booleans, text, complex values, and non-scalar arrays.
• Continue accepting ordinary Python/NumPy real scalars and 0-D real arrays.
• Add regression tests for both invalid and valid scalar inputs.

The branch is based directly on current main and changes only the discrete-state compatibility validator and its focused regression tests.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Max errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no		no	7.67s
✅ JSON	prettier	7	0	0		0	0.71s
✅ JSON	v8r	7		0		0	4.78s
✅ MARKDOWN	markdownlint	68	0	0		0	1.95s
✅ MARKDOWN	markdown-table-formatter	68	0	0		0	0.4s
✅ PYTHON	black	2036	1	0		0	66.64s
✅ PYTHON	isort	2036	5	0		0	3.0s
✅ REPOSITORY	betterleaks	yes		no		no	1.37s
✅ REPOSITORY	checkov	yes		no		no	34.03s
✅ REPOSITORY	git_diff	yes		no		no	0.27s
✅ REPOSITORY	secretlint	yes		no		no	107.24s
✅ REPOSITORY	syft	yes		no		no	3.56s
✅ REPOSITORY	trivy-sbom	yes		no		no	3.04s
✅ YAML	prettier	11	0	0		0	0.88s
✅ YAML	v8r	11		0		0	18.14s
✅ YAML	yamllint	11		0		0	1.04s

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