ludic.ui: <option disabled="{...}"> - a select steps past it, clamps off it and greys the arrow toward it

- The arrows, a press on the select and the pad step past a disabled option (ct_opt_step), wrapping
  as before.
- A value naming a disabled option is shown as the nearest enabled one (the lower of two as near) and
  set to it once the build is done: an event fired while the tree is built is cleared with the frame's,
  so the clamp is queued (ct_clamp_n / _i) and fired after nt_fired_clear.
- The < or > whose next option is disabled is drawn disabled (its part's :disabled), so a cycler shows
  where the options stop being on; it still steps past them.
- ct_build_select moves to controls_opts.ludic with the rest (controls_build.ludic 119 -> 104 lines).

Golden ui_select_disabled: options 3 and 4 disabled, a value of 4 clamps to 2, > is drawn disabled
there, > wraps to 0 and < from 0 steps back to 2. The 38 ui examples pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.ui/frame.ludic

@@ -5,6 +5,7 @@
 
 export function ui_show(ui_st: mut UiState, screen: string, view: UiView, x: float, y: float, w: float, h: float) -> void {
   in_read(ui_st)
+  ct_opt_forget(ui_st)                           # a clamp found by a build this frame did not show
   dv_before(ui_st)
   ui_st.an_frame += 1
   ui_viewport(ui_st, w, h)
@@ -12,6 +13,7 @@ export function ui_show(ui_st: mut UiState, screen: string, view: UiView, x: flo
   if root == null { return }
   ui_place(ui_st, root, x, y, w, h)
   nt_fired_clear(ui_st)
+  ct_opt_flush(ui_st)                            # a select's value on a disabled option, set now
   sc_undo(root)
   sc_update(ui_st, root)
   fr_pointer(ui_st, root)