Sunset the dedicated cutscene asset loader and the item pool

Cutscenes now load through the generic ASSET_LOADER_TYPE_JSON loader
and parse straight into fixed static buffers via new cutsceneParseDoc/
cutsceneParseItem/cutsceneCountItems helpers (cutscene.c), removing the
bespoke ASSET_LOADER_TYPE_CUTSCENE pipeline entirely. Only one cutscene
(plus one INSERT target) is ever resident, so each resolve locks,
steals the parsed doc, unlocks, and force-reaps immediately - fixing a
stale-cache-reuse bug where revisiting a cutscene name after a
different one could return data from the shared buffer's previous
occupant.

ENTITY_WALK_TO and MAP_AREA_WAIT now store their waypoints/area ids in
fixed-size arrays inline on their own item struct instead of a shared
bump-allocated pool, so pool/poolOffset are gone from every item type's
Load callback. cutscene_t.dataSize (and the CUTSCENE(...) macro's SIZE
parameter) is removed along with it - it sized entries out of that same
now-deleted pool and had no other reader.

NPC #4's battletest cutscene and the main menu's cutscene now resolve
their target by name on interact instead of eagerly at init, so a
resolved-once pointer is never held past the point its backing buffer
can be reused for something else.

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

test/rpg/entity/test_entityinteract.c

@@ -17,8 +17,7 @@ static const cutsceneitem_t CUTSCENE_TEST_INTERACT_ITEMS[] = {
 static const cutscene_t CUTSCENE_TEST_INTERACT = {
   .items = CUTSCENE_TEST_INTERACT_ITEMS,
   .itemCount = 1,
-  .pause = CUTSCENE_PAUSE_NONE,
-  .dataSize = 0
+  .pause = CUTSCENE_PAUSE_NONE
 };
 
 static entity_t *player;