feat(editor): add WSCT JSON round-trip (--export/--import-wsct-json)

Closes the editing loop on the spell-cast-time bucket catalog:
dump a .wsct to JSON, hand-edit baseCastMs / perLevelMs / clamp
bounds (retune a Pyroblast bucket from 3000ms to 2800ms across
every spell that references it), re-import to a byte-identical
binary. The exporter emits both castKind (int 0..4) and the
human-readable castKindName ("instant", "cast", "channel",
"delayed", "charge"); the importer accepts either.

Verified byte-identical round-trip on all three presets
(starter / channel / ramp). CLI flag count 897 -> 899.

tools/editor/cli_arg_required.cpp

@@ -211,6 +211,7 @@ const char* const kArgRequired[] = {
     "--export-wsrg-json", "--import-wsrg-json",
     "--gen-sct", "--gen-sct-channel", "--gen-sct-ramp",
     "--info-wsct", "--validate-wsct",
+    "--export-wsct-json", "--import-wsct-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",