feat(editor): add WMOU JSON round-trip authoring workflow

Closes the WMOU open-format loop with --export-wmou-json /
--import-wmou-json, mirroring the JSON pairs added for
every other novel binary format. All 26 binary formats
added since WOL now have full JSON round-trip authoring.

Each mount round-trips all 14 scalar fields. Three
enum-typed fields emit dual int + name forms:
  • mountKind  (ground / flying / swimming / hybrid / aquatic)
  • factionId  (both / alliance / horde)
  • categoryId (common / epic / racial / event / achievement /
                 pvp / quest / class)

Verified byte-identical round-trip on the flying preset
(4 mounts spanning common/epic/achievement/pvp tiers with
full WSPL spell + WIT item + WSKL riding skill cross-refs
preserved through the JSON layer).

Adds 2 flags (630 documented total now).

tools/editor/cli_arg_required.cpp

@@ -94,6 +94,7 @@ const char* const kArgRequired[] = {
     "--export-wsea-json", "--import-wsea-json",
     "--gen-mounts", "--gen-mounts-racial", "--gen-mounts-flying",
     "--info-wmou", "--validate-wmou",
+    "--export-wmou-json", "--import-wmou-json",
     "--gen-bg", "--gen-bg-classic", "--gen-bg-arena",
     "--info-wbgd", "--validate-wbgd",
     "--gen-weather-temperate", "--gen-weather-arctic",