refactor(editor): extract zone-creation handlers into cli_zone_create.cpp

Moves the two zone-creation handlers (--scaffold-zone,
--mvp-zone) out of main.cpp into a new cli_zone_create.{hpp,cpp}
module. Both kickstart a new authoring session by generating a
new zone directory under custom_zones/ — empty for scaffold,
populated with one of each content type (creature + object +
quest with objective + reward) for mvp. Each goes terrain +
manifest, then mvp adds the demo content positioned at the
tile center.

main.cpp shrinks by 155 lines (4,771 to 4,616).

tools/editor/cli_zone_create.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the zone-creation handlers. Both kickstart a new
+// authoring session by generating a new zone directory under
+// custom_zones/ — empty for --scaffold-zone, populated with
+// one of each content type for --mvp-zone.
+//   --scaffold-zone   minimal valid empty zone (terrain + manifest)
+//   --mvp-zone        scaffold + 1 creature + 1 object + 1 quest
+//
+// Returns true if matched; outRc holds the exit code.
+bool handleZoneCreate(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee