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

Closes the JSON round-trip gap on the spell visual kit catalog
format shipped this batch. --export-wsvk-json emits all 12
scalar fields and 4 model-path strings. WSVK has no enum
fields, so the JSON mapping is a straight-through dump with
no name-form widening. --import-wsvk-json parses it back,
defaulting unset fields to 0/empty. Verified byte-identical
round-trip on all three preset emitters (starter / combat /
utility). 731 documented CLI flags.

tools/editor/cli_arg_required.cpp

@@ -140,6 +140,7 @@ const char* const kArgRequired[] = {
     "--export-wani-json", "--import-wani-json",
     "--gen-svk", "--gen-svk-combat", "--gen-svk-utility",
     "--info-wsvk", "--validate-wsvk",
+    "--export-wsvk-json", "--import-wsvk-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",