Brushes that were verified to be impacted by this:
* Clay
* Smooth
* Cloth
Brushes that were verified to not be impacted:
* Draw
* Blob
There is some dependency within the brush code that expects that the
`ss.deform_cos` variable is not updated during the middle of the stroke.
This commit only deals with fixing the immediate user-facing issue, for
a longer-term or more comprehensive fix, it is likely that these values
should not be touched at all inside the `sculpt_update_object` function
but should instead be initialized somewhere else so that the lifecycle
is more obvious and maintainable.
Pull Request: https://projects.blender.org/blender/blender/pulls/126803
bb97131bb9