Tooltips should maybe inherit the style of the parent?

I think it makes sense if the style of a tooltip (`on_hover_ui`) would inherit the `Style` of the parent `Ui`. Maybe?

Start by tracing the `on_hover_ui` tooltip entry point and how `Style` is applied to the parent `Ui`. Clarify the intended inheritance behavior and its edge cases before choosing an implementation. Done means the behavior is agreed, implemented, and covered by tests for tooltip styling.

Written by the indexing model from the issue text.