migrate to the new for-loop syntax

Drop the ':' before captures (for xs (x) / for 0..n (i)); the index
capture becomes the trailing open range (for xs, 0.. (x, i)). 136
headers across 26 files, mechanical.

Five headless tests (banner_layout, hit_test, swipe_commit,
swipe_intent, swipe_reshuffle) also gain a direct
#import "modules/ui/types.sx" — they named Point/Frame through a
transitive import, which bare visibility no longer permits.

Gates: sx build --target ios-sim main.sx links; tools/run_tests.sh
23/23.

tests/fx_combo.sx

@@ -21,7 +21,7 @@ main :: () -> s32 {
     expect_level : [10]s64 = .{ 0, 0, 1, 2, 3, 4, 4, 4, 4, 4 };
 
     prev : s64 = -1;
-    for 0..10: (depth) {
+    for 0..10 (depth) {
         lvl := fx_combo_level(depth);
         font := fx_popup_font(depth);
         combo := depth > 1;
@@ -45,7 +45,7 @@ main :: () -> s32 {
     // larger and the font never shrinks as the cascade deepens.
     if fx_popup_font(1) != FX_POPUP_FONT { print("FAIL: single-clear popup not plain font\n"); return 1; }
     pf : f32 = 0.0;
-    for 2..10: (depth) {
+    for 2..10 (depth) {
         f := fx_popup_font(depth);
         if f <= FX_POPUP_FONT { print("FAIL: combo popup not larger than plain at depth {}\n", depth); return 1; }
         if depth > 2 and f < pf { print("FAIL: popup font shrank at depth {}\n", depth); return 1; }