GUI: add F2 preview shell with dummy controls

First vertical slice for the custom ISurface GUI:

- window/sidebar/content shell with Movement, Combat, Visuals, Weapons and
  System categories;
- cards with dummy Active/Bind, collapsible settings, toggles, sliders,
  buttons, bind capture, scrolling and tooltips;
- native OS cursor by releasing SDL relative mode; reasserted while open;
- F2 toggles the preview; Insert still opens the old text tree;
- while the GUI is open, do_move freezes movement/buttons/impulses/view and
  skips combat features; ESP and the speed graph keep drawing.

Dummy controls do not touch the real config yet. The text menu is removed
after feature parity in the next pass.

0 files changed, 0 insertions, 0 deletions