refactor(editor): extract 10 mesh edit ops into cli_mesh_edit.cpp

Moves the WOM mesh editing/transform handlers out of main.cpp:

  --add-texture-to-mesh   --scale-mesh
  --translate-mesh        --strip-mesh
  --rotate-mesh           --center-mesh
  --flip-mesh-normals     --mirror-mesh
  --smooth-mesh-normals   --merge-meshes

These are the post-generation manipulators (load → mutate → save)
distinct from the geometry generators in cli_gen_mesh.cpp and
the heightmap I/O in cli_mesh_io.cpp.

main.cpp drops 20,741 → 20,005 lines (-736). Behavior verified
by piping a fresh cube through scale → translate → center.

tools/editor/cli_mesh_edit.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the WOM mesh editing/transform commands:
+//   --add-texture-to-mesh     --scale-mesh
+//   --translate-mesh          --strip-mesh
+//   --rotate-mesh             --center-mesh
+//   --flip-mesh-normals       --mirror-mesh
+//   --smooth-mesh-normals     --merge-meshes
+//
+// Returns true if matched; outRc holds the exit code.
+bool handleMeshEdit(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee