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.

main.sx

@@ -183,8 +183,8 @@ parse_s64 :: (s: string) -> s64 {
 // trial swaps inside `swap_legal` are reverted, so the board is left unchanged.
 illegal_swaps :: (board: *Board) -> List(Swap) {
     result := List(Swap).{};
-    for 0..BOARD_ROWS: (row) {
-        for 0..BOARD_COLS: (col) {
+    for 0..BOARD_ROWS (row) {
+        for 0..BOARD_COLS (col) {
             here := Cell.{ col = col, row = row };
             if col + 1 < BOARD_COLS {
                 right := Cell.{ col = col + 1, row = row };
@@ -222,7 +222,7 @@ frame :: () {
         g_pipeline.resize(fc.viewport_w, fc.viewport_h);
     }
 
-    for g_plat.poll_events(): (*ev) {
+    for g_plat.poll_events() (*ev) {
         inline if OS != .ios {
             if ev == {
                 case .key_up: (e) {
@@ -277,7 +277,7 @@ frame :: () {
                 mv := @g_anim.move;
                 total := g_anim.total();
                 last := mv.rounds.len - 1;
-                for 0..BOARD_CELLS: (i) {
+                for 0..BOARD_CELLS (i) {
                     m := delivering_round(mv, i, last);
                     if m >= 0 {
                         col := i % BOARD_COLS;