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.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/hl2h.h b/src/hl2h.h
index 285b591..11b9014 100644
--- a/src/hl2h.h
+++ b/src/hl2h.h
@@ -230,6 +230,11 @@ bool head_position(int idx, Vector &out);
 int aim_points(int idx, unsigned group_mask, Vector *out, int max);
 
 void outer_draw();
+void menu_force_close();
+void gui_handle_input();
+void gui_draw();
+bool gui_is_open();
+QAngle gui_frozen_view();
 // ISurface pointer (defined in menu.cpp, used for drawing tests)
 struct ISurface;
 extern ISurface *g_surface;