docs(skill): recommend ruff --fix workflow for PRs failing ruff check

[priya-sundaram-dev]

Per @cclauss's request in #15081, this adds a When a PR fails ruff check subsection to .github/skills/code-review/SKILL.md.

It gives reviewers a fixed, repeatable procedure:

1. Try ruff check --fix file_path.py (safe fixes) — if the file passes, recommend that.
2. Otherwise try ruff check --fix --unsafe-fixes file_path.py — if it passes and the diff genuinely preserves behavior, recommend that and note it needed --unsafe-fixes.
3. If neither works (or the unsafe fix changes behavior), describe the remaining violations and the manual fix.

It also reminds the reviewer to quote the exact rule codes (e.g. UP047, RUF100) and paste the command they ran, so the author knows exactly what to do.

Refs #15081.

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 file (.github/skills/code-review/SKILL.md); it is a documentation-only change, not a new algorithm.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.

[algorithms-keeper]

Closing this pull request as invalid

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