Fix correctness issues found in repository audit

[keon]

Summary

• fix Sudoku subgrid validation, extended GCD, maximum tree path sum, recursive rotated search, BST deletion, ordered stack insertion, and transitive closure
• repair four broken tree-module imports and export inorder traversal from algorithms.tree
• correct integer math behavior and make repeated tree construction state-safe
• add focused regression coverage and synchronize all executable documentation examples
• make clique output deterministic across hash seeds
• pin CI and release actions to immutable Node 24 commits, reduce workflow permissions, enforce doctests, and add educational cryptography warnings

Validation

• 591 tracked unit and regression tests passed locally
• 478 doctests passed locally, 1 skipped
• Ruff passed
• clean sdist and wheel build succeeded
• installed-wheel sweep imported all 403 modules with zero failures
• GitHub Actions passed on Python 3.10, 3.11, 3.12, and 3.13

Notes

The repository-wide MyPy backlog remains separate from these runtime and release fixes; this PR does not hide it with ignores or configuration suppressions.