BEHAVIOR: use Ruff rule names, not codes

[redeboer]

Closes #676

❗ Behavioral changes

• The Ruff configuration generated by check-dev-files now identifies rules by name instead of by code, both in [tool.ruff.lint] ignore and in [tool.ruff.lint.per-file-ignores] — any-type instead of ANN401, undocumented-public-module instead of D100, private-member-access instead of SLF001, and so on. Prefix selectors that have no single rule name (ANN, D, DOC, FBT, PTH, T20, …) remain as codes.
• Selecting rules by name requires Ruff's preview mode. The policy already writes preview = true to [tool.ruff], so downstream repositories need no extra opt-in, but a repository that disables preview will now fail with Invalid selector.
• docs/conf.py is now granted builtin-variable-shadowing on top of undocumented-public-module, so Sphinx's copyright = ... assignment no longer needs an inline suppression.
• Code-based ignores that already exist in a downstream pyproject.toml are merged rather than rewritten, so those configurations will list both the old code and the new name until the codes are pruned by hand.

Squash commit messages

* BEHAVIOR: ignore `builtin-variable-shadowing` in `docs/conf.py`
* MAINT: migrate `noqa` comments to `ruff: ignore` syntax