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

Closes the JSON round-trip gap on the PvP rank catalog
format shipped this batch. --export-wpvp-json emits all 12
scalar fields plus a dual int + name form for rankKind (5
values) so hand-edits can use either representation.
--import-wpvp-json defaults bracket level to 1..80 (no level
gate) when omitted — matches the typical case for vanilla
honor ranks which weren't level-gated beyond the cap.
Verified byte-identical round-trip on all three preset
emitters (starter / alliance vanilla 9-rank ladder / arena
5-tier ladder). 835 documented CLI flags.

tools/editor/cli_arg_required.cpp

@@ -184,6 +184,7 @@ const char* const kArgRequired[] = {
     "--export-wchf-json", "--import-wchf-json",
     "--gen-pvp", "--gen-pvp-alliance", "--gen-pvp-arena",
     "--info-wpvp", "--validate-wpvp",
+    "--export-wpvp-json", "--import-wpvp-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",