fix(sorts): make power_sort generic over Comparable items

[wanjinhao1]

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.
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Part of #15234 (does not close the tracking issue).

What

• Adds a Comparable protocol (__lt__ only) and a PEP 695 TypeVar bound so power_sort accepts any iterable of mutually comparable items (Iterable[T] → list[T]) instead of a bare list. The key path stays Callable[[T], Any] per the audit note in the tracker discussion.
• Rewrites the run-detection and merge comparisons to use only < (the protocol guarantees nothing else): the ascending-run check >= becomes not (... < ...) and the merge tie left <= right becomes not (right < left), which preserves stability for total orders.
• Adds a mixed-type failure doctest (power_sort([1, "a"]) → TypeError).
• Registers power_sort in the shared SORTS battery and the non-comparable rejection list in tests/test_sorts.py.

Why

power_sort.py is one of the remaining unchecked comparison sorts in the #15234 checklist, with no open PR and no assignee.

Validation

• python3 -m doctest sorts/power_sort.py — all doctests pass (including the new TypeError case)
• python3 -m pytest tests/test_sorts.py -q — 395 passed (includes power_sort across the full shared CASES battery and the [1, "a"] rejection test)

Note: one algorithm per PR per the tracker guidance. This PR was completed with AI assistance under the supervision of the account owner (@wanjinhao1) — happy to address any review feedback.

[algorithms-keeper]

Closing this pull request as invalid

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