A new map is playable at once (scenes re-read on its first save); edit test covers it; mod cover

locale/ui_en.properties

@@ -19,7 +19,7 @@ tools/rpg_editor/redo = Redo
 tools/rpg_editor/redo_tip = Redo (Ctrl+Y)
 tools/rpg_editor/play = Play
 tools/rpg_editor/play_tip = Save and walk the map from its spawn in the running game
-tools/rpg_editor/play_no_scene = Scene "{0}" is not loaded yet: reload the mods (Ctrl+Shift+R) after creating a map.
+tools/rpg_editor/play_no_scene = The game does not know scene "{0}": check scenes/{0}.json in the map's mod.
 tools/rpg_editor/scene_created = scene {0} created
 tools/rpg_editor/section_palette = Palette
 tools/rpg_editor/section_map = Map