refactor(editor): extract simple texture helpers into cli_texture_helpers.cpp

Moves the two basic texture-helper handlers (--gen-texture,
--add-texture-to-zone) out of main.cpp into a new
cli_texture_helpers.{hpp,cpp} module. The first synthesizes
solid hex / checker / grid PNG placeholders; the second
imports an existing PNG into a zone with optional rename and
idempotent re-run support (skip if bytes already match).
Both complement the procedural pattern generators in
cli_gen_texture (which handles the 43 named patterns).

main.cpp shrinks by 196 lines (2,022 to 1,826) and finally
drops below 2K lines.

tools/editor/cli_texture_helpers.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the simple texture-helper handlers — placeholder
+// generation and PNG import workflows that complement the
+// procedural pattern generators in cli_gen_texture.
+//   --gen-texture           solid hex / checker / grid PNG
+//   --add-texture-to-zone   import an existing PNG into a zone
+//
+// Returns true if matched; outRc holds the exit code.
+bool handleTextureHelpers(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee