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/cascade_rounds.sx

@@ -57,7 +57,7 @@ main :: () -> s32 {
 
     // Deep chain: the cue tail clamps at combo5 for round >= 5 (cascade_cue_index).
     print("-- deep-chain cue clamp --\n");
-    for 1..8: (r) { print("round {} -> {}\n", r, cascade_cue_name(cascade_cue_index(r))); }
+    for 1..8 (r) { print("round {} -> {}\n", r, cascade_cue_name(cascade_cue_index(r))); }
 
     print("ok: one ascending combo cue per cascade round, clamped at combo5\n");
     return 0;