refactor(editor): extract item-export handlers into cli_items_export.cpp

Moves the three item-export handlers (--export-zone-items-md,
--export-project-items-md, --export-project-items-csv) out of
main.cpp into a new cli_items_export.{hpp,cpp} module. All
three render items.json data as human-readable Markdown / CSV
reports for design docs, PR descriptions, GitHub Pages, and
spreadsheet pivot-table workflows.

main.cpp shrinks by 262 lines (5,349 to 5,087).

tools/editor/cli_items_export.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the item-export handlers — render items.json as
+// human-readable Markdown / CSV reports for design docs and
+// pivot-table workflows.
+//   --export-zone-items-md       per-zone Markdown by quality
+//   --export-project-items-md    project-wide Markdown rollup
+//   --export-project-items-csv   project-wide CSV (zone in col 1)
+//
+// Returns true if matched; outRc holds the exit code.
+bool handleItemsExport(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee