sorts: make heap sort support comparable items - #15291

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.)

Priya said:

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