feat(editor): add WSRG JSON round-trip (--export/--import-wsrg-json)

Closes the editing loop on the spell-range bucket catalog: dump a
.wsrg to a JSON sidecar, hand-edit the buckets (rename, retune
yards, recolor HUD indicator), re-import to a byte-identical
binary. The exporter emits both the int rangeKind (0..6) and the
human-readable rangeKindName ("self", "melee", "short", "ranged",
"long", "very-long", "unlimited"); the importer accepts either,
so JSON sidecars stay readable without losing the canonical binary
encoding.

Verified byte-identical round-trip on all three presets (starter,
ranged, friendly). CLI flag count 890 -> 892.

tools/editor/cli_arg_required.cpp

@@ -208,6 +208,7 @@ const char* const kArgRequired[] = {
     "--export-wqso-json", "--import-wqso-json",
     "--gen-srg", "--gen-srg-ranged", "--gen-srg-friendly",
     "--info-wsrg", "--validate-wsrg",
+    "--export-wsrg-json", "--import-wsrg-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",