[sshnox]

Describe your change

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues, then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

Summary

• Replace the deprecated np.char.chararray grid with a fixed-width Unicode ndarray.
• Preserve the existing single-character grid behavior while avoiding NumPy's deprecated chararray class.

Validation

• python3 -m compileall -q graphs/multi_heuristic_astar.py
• Runtime smoke test for do_something with deprecation warnings treated as errors.
• uv run --with ty ty check --exclude-scripts no longer reports the deprecated diagnostic.