RUF076: should not fire in conftest.py by default (autouse is the standard pattern there)

## Summary `RUF076` (pytest-fixture-autouse) discourages `autouse=True` in pytest fixtures, but fires in `conftest.py` files by default. This is problematic because `conftest.py` is precisely where `autouse=True` fixtures are most appropriate and widely used — it's the standard pytest pattern for applying shared setup across a test directory. The rule's own documentation acknowledges this tension: > This is a pedantic rule that restricts a valid pytest pattern. And even suggests a workaround to *only* apply it in conftest.py: ```toml [tool.ruff.lint.per-file-ignores] "!**/conftest.py" = ["RUF076"] ``` But this inverts the correct default. The rule should **not** fire in `conftest.py` by default — or at minimum, there should be a configuration option to scope it to non-conftest files only. Autouse fixtures in conftest.py are the documented, recommended pytest approach for directory-scoped setup (e.g., environment variables, database cleanup, logging config). ## Reproduction ```python # conftest.py import pytest @pytest.fixture(autouse=True) def setup_test_env() -> None: """Standard conftest autouse fixture for test environment setup.""" ... ``` ```toml [tool.ruff] lint.extend-select = ["RUF"] lint.preview = true ``` ``` $ ruff check conftest.py RUF076: Avoid using `autouse=True` in `pytest.fixture` decorators ``` ## Expected behavior Either: 1. `RUF076` should not fire in `conftest.py` by default (since that's where autouse is most appropriate), OR 2. The default should be inverted: only fire in conftest.py if explicitly configured, and fire in test files by default (where autouse is actually problematic) ## Ruff version ``` ruff 0.15.18 ``` ## Context The original rule request (#12491) specifically called out conftest.py as problematic, but in practice, `autouse` in conftest is the standard pytest pattern documented at: - https://docs.pytest.org/en/stable/how-to/fixtures.html#autouse-fixtures-fixtures-you-don-t-have-to-request - https://docs.pytest.org/en/stable/how-to/fixtures.html#conftest-py-sharing-fixtures-across-tests The rule is useful for discouraging autouse in individual test files (where it's truly confusing), but not in conftest.py where it's expected behavior.