Assert NULL pointer/marker args in cutscenesystem.c entry points

Matches the existing assertNotNull convention in cutscene.c
(cutsceneAppend/cutsceneParseDoc etc.) - these are internal-API
preconditions on trusted callers, not untrusted input.

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

src/dusk/rpg/cutscene/cutscenesystem.c

@@ -45,6 +45,8 @@ void cutsceneSystemPrepare(
   entity_t *interact,
   entity_t *interacted
 ) {
+  assertNotNull(cutscene, "Cutscene cannot be NULL");
+
   CUTSCENE_SYSTEM.scene = cutscene;
   CUTSCENE_SYSTEM.pause = cutscene->pause;
   CUTSCENE_SYSTEM.entityInteract = interact;
@@ -75,11 +77,14 @@ void cutsceneSystemStartCutsceneAndGoToMarker(
   cutscene_t *cutscene,
   const char_t *marker
 ) {
+  assertNotNull(marker, "Marker cannot be NULL");
+
   cutsceneSystemPrepare(cutscene, NULL, NULL);
   cutsceneGoTo(marker);
 }
 
 void cutsceneSystemInsertCutscene(const cutscene_t *cutscene) {
+  assertNotNull(cutscene, "Cutscene cannot be NULL");
   assertNotNull(
     CUTSCENE_SYSTEM.scene,
     "cutsceneSystemInsertCutscene called with no cutscene running"
@@ -93,6 +98,8 @@ void cutsceneSystemInsertCutscene(const cutscene_t *cutscene) {
 }
 
 void cutsceneSystemLoad(const char_t *file) {
+  assertNotNull(file, "File cannot be NULL");
+
   char_t path[ASSET_FILE_NAME_MAX];
   stringFormat(path, sizeof(path), "cutscenes/%s", file);
 
@@ -231,6 +238,8 @@ const char_t * cutsceneSystemGetTextCache(void) {
 }
 
 void cutsceneSystemSetTextCache(const char_t *text) {
+  assertNotNull(text, "Text cannot be NULL");
+
   stringCopy(
     CUTSCENE_SYSTEM.textCache, text, CUTSCENE_TEXT_CACHE_MAX - 1
   );
@@ -277,6 +286,7 @@ void cutsceneSystemNext() {
 }
 
 void cutsceneGoTo(const char_t *name) {
+  assertNotNull(name, "Name cannot be NULL");
   assertNotNull(
     CUTSCENE_SYSTEM.scene, "cutsceneGoTo called with no cutscene running"
   );