Reject complex SE2 UKF inputs

[FlorianPfaff]

Bug

SE2UKF accepted complex-valued dual-quaternion states, noise distributions, and measurements whenever their shapes, finiteness, and real-valued geometric checks happened to pass.

For example, the measurement [1+0j, 0, 1j, 0] has a valid unit rotation part and finite entries, so the existing validator accepted it. The identity update then propagated the imaginary translation into an otherwise real filter state; with the default state and 0.1 I measurement covariance, the posterior translation becomes approximately 0.909i.

Complex dual-quaternion coordinates are outside the real SE(2) state space represented by this filter.

Fix

• detect complex NumPy/JAX arrays and PyTorch tensors before geometric validation
• reject complex state and noise means
• reject complex state and noise covariances
• reject complex measurements before any update calculations
• preserve the existing filter state when measurement validation fails

Regression coverage

• a complex measurement raises ValueError and leaves the posterior mean and covariance unchanged
• a manually corrupted complex filter-state mean is rejected by the public setter

Validation

• branch is based on the current main head and is zero commits behind
• final comparison is limited to se2_ukf.py and one focused regression-test file
• an isolated numerical reproduction confirmed the pre-fix complex posterior contamination
• repository CI should provide the complete NumPy, JAX, PyTorch, lint, packaging, and documentation matrix

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no	no	29.58s
✅ JSON	prettier	7	0	0	0	1.11s
✅ JSON	v8r	7		0	0	5.14s
✅ MARKDOWN	markdownlint	68	0	0	0	1.77s
✅ MARKDOWN	markdown-table-formatter	68	0	0	0	0.51s
✅ PYTHON	black	1828	65	0	0	96.22s
✅ PYTHON	isort	1828	99	0	0	2.84s
✅ REPOSITORY	betterleaks	yes		no	no	2.44s
✅ REPOSITORY	checkov	yes		no	no	57.0s
✅ REPOSITORY	gitleaks	yes		no	no	17.34s
✅ REPOSITORY	git_diff	yes		no	no	0.36s
✅ REPOSITORY	secretlint	yes		no	no	85.04s
✅ REPOSITORY	syft	yes		no	no	6.58s
✅ REPOSITORY	trivy-sbom	yes		no	no	7.23s
✅ REPOSITORY	trufflehog	yes		no	no	32.09s
✅ YAML	prettier	11	0	0	0	0.75s
✅ YAML	v8r	11		0	0	12.81s
✅ YAML	yamllint	11		0	0	0.45s

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