Complete MHT tracker and backend fixes

[FlorianPfaff]

Summary

• complete and export the multi-hypothesis tracker implementation
• document the tracker in the API overview
• add backend contract fixes for high-rank operations and diagonal handling
• preserve remaining PyTorch random scalar behavior from the bugfix patch

Notes

• Some CLI and diagnostics hunks from pyrecest_bugfixes.patch were already present on current main; only the remaining missing changes were applied.

Verification

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

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ COPYPASTE	jscpd	yes		no	no	35.05s
✅ MARKDOWN	markdownlint	1	0	0	0	0.8s
✅ MARKDOWN	markdown-table-formatter	1	0	0	0	0.63s
✅ PYTHON	black	9	1	0	0	2.62s
✅ PYTHON	isort	9	2	0	0	0.49s
✅ REPOSITORY	checkov	yes		no	no	31.55s
✅ REPOSITORY	gitleaks	yes		no	no	13.98s
✅ REPOSITORY	git_diff	yes		no	no	0.05s
✅ REPOSITORY	secretlint	yes		no	no	13.97s
✅ REPOSITORY	syft	yes		no	no	5.01s
✅ REPOSITORY	trivy-sbom	yes		no	no	3.61s
✅ REPOSITORY	trufflehog	yes		no	no	20.62s

Notices

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[github-actions]

Test Results

    10 files  ± 0      10 suites  ±0   2h 33m 37s ⏱️ - 4m 31s
 2 153 tests + 7   2 149 ✅ + 7      4 💤 ± 0  0 ❌ ±0 
21 961 runs  +70  18 239 ✅ +45  3 722 💤 +25  0 ❌ ±0 

Results for commit a0b8b61. ± Comparison against base commit 2e7cda3.

♻️ This comment has been updated with latest results.