Function clamp_scroll_offsets 

pub fn clamp_scroll_offsets(
    children_q: Query<'_, '_, (&ChildOf, &Transform)>,
    scrolls: Query<'_, '_, (Entity, &Transform, &mut Scroll, &mut ScrollOffset)>,
)

Clamp every ScrollOffset to [0, content - viewport] per axis, with macOS-style rubber-band overshoot driven by crate::physics::RUBBER_BAND_STIFFNESS. Runs after layout so child Transforms reflect the current content extent.

Content extent is computed as the bounding box of the scroll container’s direct children - virtualized <for> blocks set their own size to rows x row_h, so the bbox correctly reflects the scrollable region.

Rubber-band model: when stiffness > 0, an offset past the bound is pulled back via bound + overflow / (1 + stiffness * |overflow|) (a Hooke spring approximation). When stiffness is 0 (Windows / Linux defaults), the offset hard-clamps and velocity is zeroed on the clamped axis so inertial flings don’t keep pumping into the wall - matching the pre-rubber-band behaviour.