[Maintenance] [th01] Move the boss post-defeat palette to the palette header

Part of P0229, funded by Ember2528.

th01/main/boss/boss.hpp

@@ -60,9 +60,6 @@ void boss_hit_update_and_render(
 	pixel_t shot_hitbox_h_minus_shot_h = 0
 );
 
-// Palette to fade to after the white boss defeat flash.
-extern Palette4 boss_post_defeat_palette;
-
 // Individual bosses
 // -----------------
 

th01/main/boss/defeat.cpp

@@ -22,6 +22,7 @@
 #include "th01/main/player/player.hpp"
 #include "th01/shiftjis/routesel.hpp"
 #include "th01/main/boss/boss.hpp"
+#include "th01/main/boss/palette.hpp"
 #include "th01/main/boss/entity_a.hpp"
 #include "th01/main/boss/defeat.hpp"
 #include "th01/main/stage/stages.hpp"

th01/main/boss/palette.hpp

@@ -3,6 +3,9 @@
 // MODDERS: Merge with the [stage_palette].
 extern Palette4 boss_palette;
 
+// Palette to fade to after the white boss defeat flash.
+extern Palette4 boss_post_defeat_palette;
+
 // Overwrites [boss_palette] with [z_Palettes].
 void boss_palette_snap(void);