Resizable Panel stores and paints using overflowed inner rect instead of clamped panel rect

[enomado]

When a resizable Panel/SidePanel contains overflowing content, the visible panel is clipped to panel_rect, but the code later stores state and paints the separator using inner_response.response.rect.

In practice this can make the resize boundary behave as if the panel were wider than the visible clipped area:

• the resize line appears at the far edge of the hidden overflowed content
• hover/drag for the panel edge feels offset from the visible panel boundary
• the persisted panel size can reflect the overflowed inner rect instead of the clamped panel rect

I verified the same logic is still present in egui 0.34.1 in src/containers/panel.rs.

The minimal fix that solved it for me locally was:

let rect = inner_response.response.rect.intersect(panel_rect);

instead of:

let rect = inner_response.response.rect;

That keeps cursor updates, PanelState, and separator painting aligned with the actual visible/clamped panel bounds.

If helpful, I can open a PR with this minimal change.