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

Closes the WSKL open-format loop with --export-wskl-json /
--import-wskl-json, mirroring the JSON pairs added for
every other novel binary format. All 13 binary formats
added since WOL now have full JSON round-trip authoring.

Each skill round-trips all 8 scalar fields (skillId, name,
description, categoryId, canTrain, maxRank, rankPerLevel,
iconPath). The categoryId emits dual int + name forms so a
hand-author can write "profession" / "weapon" / "language"
instead of the int values.

Verified byte-identical round-trip on the professions
preset (12 entries: 9 primary + 3 secondary professions
with full canonical SkillLine IDs preserved).

Adds 2 flags (537 documented total now).

tools/editor/cli_arg_required.cpp

@@ -55,6 +55,7 @@ const char* const kArgRequired[] = {
     "--export-wlck-json", "--import-wlck-json",
     "--gen-skills", "--gen-skills-professions", "--gen-skills-weapons",
     "--info-wskl", "--validate-wskl",
+    "--export-wskl-json", "--import-wskl-json",
     "--gen-spells", "--gen-spells-mage", "--gen-spells-warrior",
     "--info-wspl", "--validate-wspl",
     "--gen-weather-temperate", "--gen-weather-arctic",