refactor(editor): extract --info-{zone,project}-density into cli_info_density.cpp

Moves the two content-density audit handlers
(--info-zone-density, --info-project-density) out of main.cpp
into a new cli_info_density.{hpp,cpp} module. Both count
creatures/objects/quests per tile to surface sparse zones
(boring) and over-stuffed ones (frame-rate bombs); the project
variant rolls per-zone numbers into a project-wide table with
per-zone averages for content-pacing reviews.

main.cpp shrinks by 201 lines (7,254 to 7,053). Both --json
output modes preserved for balance-audit pipelines.

tools/editor/cli_info_density.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the content-density audit handlers — count creatures
+// / objects / quests per tile to surface sparse zones (boring)
+// and over-stuffed ones (frame-rate bombs). Useful for content
+// pacing reviews and balance audits.
+//   --info-zone-density     per-tile bucket within one zone
+//   --info-project-density  per-zone rollup with project-wide averages
+//
+// Both support an optional trailing `--json` flag for
+// machine-readable reports.
+//
+// Returns true if matched; outRc holds the exit code.
+bool handleInfoDensity(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee