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

Closes the WFAC open-format loop with --export-wfac-json /
--import-wfac-json, mirroring the JSON pairs added for
every other novel binary format. All 11 binary formats
added since WOL now have full JSON round-trip authoring.

Each faction round-trips:
  • 13 scalar fields (id, parent, name, description, flags,
    7 ascending threshold values, baseReputation)
  • enemies[] and friends[] as JSON int arrays for trivial
    hand-edit
  • reputationFlags as dual int + string-array form
    (e.g. ["visible", "header"])

The 7 reputation thresholds round-trip exactly even though
they have non-default values in some presets — the
importer uses the canonical Hostile/Friendly/etc enum
values as defaults so a hand-author can omit the standard
thresholds and only specify custom ones.

Verified byte-identical round-trip on the alliance preset
(5 factions: Alliance header + 3 cities with reciprocal
friend lists + Defias enemy). Adds 2 flags (523 documented
total now).

tools/editor/cli_arg_required.cpp

@@ -49,6 +49,7 @@ const char* const kArgRequired[] = {
     "--export-wgot-json", "--import-wgot-json",
     "--gen-factions", "--gen-factions-alliance", "--gen-factions-wildlife",
     "--info-wfac", "--validate-wfac",
+    "--export-wfac-json", "--import-wfac-json",
     "--gen-locks", "--gen-locks-dungeon", "--gen-locks-professions",
     "--info-wlck", "--validate-wlck",
     "--gen-weather-temperate", "--gen-weather-arctic",