Add ruff and ty pre-commit hooks with CI workflow

[Copilot]

Adds standard Python linting/formatting (ruff) and type checking (ty) via pre-commit, with a GitHub Actions workflow to enforce them on PRs and pushes to main.

Changes

• .pre-commit-config.yaml — configures three hooks:

  • ruff — linting with auto-fix
  • ruff-format — code formatting
  • ty (local, pinned to 0.0.17) — type checking via ty check --ignore unresolved-import (sphinx/docutils stubs unavailable in the pre-commit env)

• .github/workflows/pre-commit.yml — runs pre-commit run --all-files on every PR and push to main using pre-commit/action@v3.0.1

• Existing source files — reformatted by ruff format to pass from day one; two lines in sphinx_config/__init__.py annotated with # type: ignore[attr-defined] to suppress ty's correct-but-unfixable complaint about the setup.extra_setup_funcs dynamic attribute pattern

Original prompt

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This section details on the original issue you should resolve

<issue_title>adding standard pre-commit tools, like ruff/ty?</issue_title>
<issue_description>Can we do the same for adding standard pre-commit tools, like ruff/ty?

Originally posted by @jpwgnr in #5 (comment)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes adding standard pre-commit tools, like ruff/ty? #7

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