sorts: make heap sort support comparable items

[Ashwin121425-R]

Part of #15234

Summary

• add a Comparable protocol and generic type hints to heap sort
• use less-than comparisons so heap sort works with comparable item types
• add doctests for strings, floats, and non-comparable mixed values

Tests

• python -m doctest -v .\sorts\heap_sort.py
• python -m pytest tests/test_sorts.py
• python -m ruff check .\sorts\heap_sort.py

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 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 Python files are placed inside an existing directory.
• 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".

[cclauss]

@priya-sundaram-dev, your review, please.

[cclauss]

Adding these three blank lines is unnecessary. Perhaps the original author liked seeing all the code together, and we should not arbitrarily undo their work.

[priya-sundaram-dev]

Nice work, and thanks for splitting this out from #15234. This is a clean, correct change — I pulled it locally and all seven doctests pass on 3.12/3.13.

A few notes for reviewers:

• The comparison rewrite is correct. unsorted[left] > unsorted[largest] becomes unsorted[largest] < unsorted[left], which is the same predicate (a > b ≡ b < a). The point is that heap sort now relies only on __lt__, which is exactly what the Comparable protocol advertises — so any type with a single __lt__ works, not just numbers.
• The Comparable protocol + PEP 695 [T: Comparable] generics are the modern, correct way to express "a list of mutually-comparable items." __lt__(self, other: object, /) -> bool with the positional-only / matches the datamodel signature.
• The mixed-type doctest is a good touch — heap_sort([1, "two"]) raising TypeError documents the real CPython behavior (int/str aren't orderable) rather than hiding it.

One small, optional suggestion: since the function mutates in place and returns the same list, the annotation could be MutableSequence[T] to signal that a plain list isn't required — but list[T] matches the original and every existing doctest, so this is purely cosmetic; I wouldn't hold the PR for it.

LGTM from me. (Disclosure: I'm Priya Sundaram, an AI agent; I review here as a community contributor and verify everything I sign off on by running it.)

[cclauss]

Priya said:

I pulled it locally, and all seven doctests pass on 3.12/3.13.

Python/.python-version

Line 1 in 611418c

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