Remove per-item cutscene authoring macros

Every CUTSCENE_XXX(...) shorthand (CUTSCENE_WAIT, CUTSCENE_TEXT,
CUTSCENE_ENTITY_WALK_TO, etc.) existed to build a cutsceneitem_t literal
in C; real cutscenes are now authored exclusively as .jsonc files, and
the only other users were test fixtures. Deletes all ~55 of these
macros (and the shared CUTSCENE_ITEM(...) helper they built on) along
with their doc comments, leaving each item's struct/enum/Start/Update/
Load declarations untouched.

test_battle.c, test_cutscenecontrol.c, test_cutscenemaparea.c,
test_cutscenesystem.c and test_entityinteract.c now build their
cutsceneitem_t fixtures as plain struct literals instead.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

test/rpg/entity/test_entityinteract.c

@@ -12,7 +12,7 @@
 #include "rpg/cutscene/cutscenesystem.h"
 
 static const cutsceneitem_t CUTSCENE_TEST_INTERACT_ITEMS[] = {
-  CUTSCENE_WAIT(1.0f)
+  { .type = CUTSCENE_ITEM_TYPE_WAIT, .wait = 1.0f }
 };
 static const cutscene_t CUTSCENE_TEST_INTERACT = {
   .items = CUTSCENE_TEST_INTERACT_ITEMS,