feat(editor): WSPK JSON round-trip closure

Adds --export-wspk-json / --import-wspk-json. spellIds serialize
as JSON int arrays preserving spellbook display order (top-to-
bottom in tab). All 3 presets (warrior/mage/rogue) byte-identical
binary roundtrip OK including Mage Frost tab [116, 122, 10] —
Frostbolt rank 1 still first, Frost Nova second, Blizzard third
after roundtrip.

Importer also restores className via implicit lookup from
classId on the export side, so a hand-edited JSON only needs
classId int — className field is informational.

CLI flag count 1335 -> 1337.

tools/editor/cli_arg_required.cpp

@@ -388,6 +388,7 @@ const char* const kArgRequired[] = {
     "--export-wmod-json", "--import-wmod-json",
     "--gen-spk-warrior", "--gen-spk-mage", "--gen-spk-rogue",
     "--info-wspk", "--validate-wspk",
+    "--export-wspk-json", "--import-wspk-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",