Harden VBRM validation and make prediction failures atomic

[FlorianPfaff]

Summary

• reject non-finite VBRM scalar/vector hyperparameters, shape states, and covariance inputs instead of allowing NaN/Inf into the recursion
• validate prediction controls before mutating state and stage the full prediction so inverse-gamma forgetting failures leave the tracker unchanged
• make update-time num_iterations use the same strict positive-integer contract as construction
• add NumPy regression tests for all of the above

Bugs fixed

1. NaN/Inf could pass positive/non-negative checks because comparisons such as nan <= 0 are false.
2. predict_linear() updated kinematics/orientation and scaled inverse-gamma parameters before checking whether forgetting drove alpha to <= 1; an exception therefore left a partially advanced tracker.
3. update(..., num_iterations=...) used int(...), silently accepting values such as True, 1.5, and "2", unlike the constructor.

The branch is based on current main at eec266f55c10304e68172057e034364ca7314375 and intentionally avoids the separate open reflection-flag fix in #5452.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Max errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no		no	6.73s
✅ JSON	prettier	7	0	0		0	0.43s
✅ JSON	v8r	7		0		0	5.38s
✅ MARKDOWN	markdownlint	68	0	0		0	1.9s
✅ MARKDOWN	markdown-table-formatter	68	0	0		0	0.31s
✅ PYTHON	black	2032	1	0		0	65.49s
✅ PYTHON	isort	2032	3	0		0	2.87s
✅ REPOSITORY	betterleaks	yes		no		no	1.2s
✅ REPOSITORY	checkov	yes		no		no	34.56s
✅ REPOSITORY	git_diff	yes		no		no	0.02s
✅ REPOSITORY	secretlint	yes		no		no	105.34s
✅ REPOSITORY	syft	yes		no		no	2.52s
✅ REPOSITORY	trivy-sbom	yes		no		no	3.07s
✅ YAML	prettier	11	0	0		0	0.53s
✅ YAML	v8r	11		0		0	17.45s
✅ YAML	yamllint	11		0		0	0.73s

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