For the brush assets project (#116337) all editors with brushes are
getting an asset shelf, and the brush tools are combined, with
individual brushes accessed in the shelf. That design seems way
overkill for UV sculpting which is just three very simple tools.
In order to avoid one editor with inconsistent use of brushes, which
would significantly increase the complexity of the system after the
brush assets merge, port the three UV sculpt tools to be regular
modal operators that don't use the brush or paint system at all.
To be clear, this is a compromise that doesn't feel ideal, but no
one could think of a better solution. Theoretically this removes
some flexibility from UV edit "sculpting", in practice it probably
won't be a noticeable change.
Pull Request: https://projects.blender.org/blender/blender/pulls/120797
e3894f0a07