Fix backend and MHT edge cases

[FlorianPfaff]

Summary

• harden backend set_diag, dot, and outer handling for rectangular and high-rank inputs
• expose MultiHypothesisTracker through the lazy filters API
• make MHT global-hypothesis validation and array-like linear updates robust
• add focused regression coverage for the affected backend and tracker paths

Validation

• git diff --check
• conflict-marker scan with rg
• python -m py_compile on changed Python files

Note: full test suites were not run per request.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no	no	34.74s
✅ MARKDOWN	markdownlint	1	0	0	0	0.75s
✅ MARKDOWN	markdown-table-formatter	1	0	0	0	0.29s
✅ REPOSITORY	checkov	yes		no	no	32.33s
✅ REPOSITORY	gitleaks	yes		no	no	16.95s
✅ REPOSITORY	git_diff	yes		no	no	0.05s
✅ REPOSITORY	secretlint	yes		no	no	15.23s
✅ REPOSITORY	syft	yes		no	no	2.52s
✅ REPOSITORY	trivy-sbom	yes		no	no	3.57s
✅ REPOSITORY	trufflehog	yes		no	no	24.14s

Notices

📣 MegaLinter 9.5.0 is out! Discover the new features and security recommendations in the release announcement. (Skip this info by defining SECURITY_SUGGESTIONS: false)

See detailed reports in MegaLinter artifacts
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

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[github-actions]

Test Results

    10 files  +    2      10 suites  +2   2h 38m 12s ⏱️ + 55m 34s
 2 153 tests ±    0   2 149 ✅ ±    0      4 💤 ±    0  0 ❌ ±0 
21 961 runs  +4 370  18 239 ✅ +2 712  3 722 💤 +1 658  0 ❌ ±0 

Results for commit fd62638. ± Comparison against base commit a9582ea.