Revise `ruff.toml`'s `extend select`

`ruff.toml` extends the selection of errors in `extend-select`, but some of those are part of the Ruff preview. I'm unsure if this is set up so that when the errors leave the preview they are enabled, or if the template should be modified so that Ruff is set to preview by default.

Rule `F401` is commented in `extend-select` so that the `try: import typing` used by libraries doesn't get removed automatically by Ruff when running `pre-commit`. However, I believe both library makers and other users would benefit from having rule `F401` uncommented. Library developers can add the comment `# noqa: F401` to their `import typing` line so that it doesn't automatically get removed by Ruff.

Start with ruff.toml and inspect the extend-select entries, including the commented F401 rule. Check how the template's pre-commit Ruff configuration handles preview rules and determine whether preview should be enabled by default. Done means the configuration reflects the decided preview policy and the intended F401 behavior.

Written by the indexing model from the issue text.