1.9.0
ENH add narwhals as dependency (#31127)
ENH remove _xfail_checks, pass directly to check runners, return structured output from check_estimator (#30149)
MNT Apply ruff/flake8-implicit-str-concat rules (ISC) (#30695)
CI: Make one tracking isssue per build for the unit-tests GHA (#32832)
MNT: externals: bump array-api-compat to v1.13 (#32962)
MNT `np.nan_to_num` -> `xpx.nan_to_num` (#32033)
MNT replace master with main (#19237)