refactor(editor): extract check-* sanity handlers into cli_check.cpp

Moves the four cross-reference / content sanity-check
handlers (--check-zone-refs, --check-zone-content,
--check-project-content, --check-project-refs) out of
main.cpp into a new cli_check.{hpp,cpp} module. Each goes
deeper than --validate (which only checks open-format file
presence) — verifying that quest NPC IDs resolve to
creatures.json entries, model paths resolve to on-disk files,
spawn positions sit inside the zone's tile bounds, etc.

main.cpp shrinks by 509 lines (2,807 to 2,298). All four
preserve --json output for CI pipelines.

tools/editor/cli_check.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the cross-reference / content sanity-check handlers.
+// Each goes deeper than --validate (which only checks open-
+// format file presence) — they verify that quest NPC IDs
+// resolve to creatures.json entries, model paths resolve to
+// on-disk files, spawn positions sit inside the zone's tile
+// bounds, etc. All four support --json for CI pipelines.
+//   --check-zone-refs        single-zone ref integrity
+//   --check-zone-content     single-zone content sanity
+//   --check-project-content  project-wide content sanity
+//   --check-project-refs     project-wide ref integrity rollup
+//
+// Returns true if matched; outRc holds the exit code.
+bool handleCheck(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee