feat/gestures: Differentiate workspace scrolling from page scrolling

In a Niri-style workflow:

- 3-finger gestures are used for workspace switching
- 2-finger gestures are used for scrolling

We need better differentiation between:

- scrolling inside a page/window
- scrolling between tracks/workspaces

One possible solution:
add a floating interaction box where scrolling over it switches tracks, otherwise normal page scrolling occurs.