Fix clabel manual argument not accepting unit-typed coordinates
Merged Mar 2026
Added self.axes.convert_xunits(x) and self.axes.convert_yunits(y) calls in add_label_near() in contour.py before applying the transform, consistent with the pattern already used in _base.py
The fix is a no-op when no unit converter is registered, so non-unit axes are completely unaffected
Filled in the existing test_clabel stub in test_datetime.py with a real test that verifies the label is placed correctly, asserting on both the label text and position