feat(editor): add WLDS JSON round-trip (export/import sidecar)

Closes the JSON round-trip gap on the loading screen catalog
format shipped last batch. --export-wlds-json emits all 11
scalar fields plus a dual int + name form for
expansionRequired so hand-edits can use either representation.
--import-wlds-json accepts either form, defaulting minLevel
to 1 and maxLevel to 80 when omitted (full level range).
Verified byte-identical round-trip on all three preset
emitters (starter / WotLK instances / raid intros with
isWideAspect=1). 856 documented CLI flags.

tools/editor/cli_arg_required.cpp

@@ -193,6 +193,7 @@ const char* const kArgRequired[] = {
     "--export-wrun-json", "--import-wrun-json",
     "--gen-lds", "--gen-lds-instances", "--gen-lds-raid",
     "--info-wlds", "--validate-wlds",
+    "--export-wlds-json", "--import-wlds-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",