feat(pipeline): WGCH global chat channel catalog (124th open format)

Novel replacement for vanilla ChatChannels.dbc + the per-server
zone-default chat-join behavior. Each WGCH entry binds one chat
channel to its access policy: PublicJoin, InviteOnly,
AutoJoinOnZone (with zoneDefaultMapId), or Moderated. Entries
also carry channelKind (Global/RealmZone/Faction/Custom),
passwordRequired, levelMin, maxMembers cap, topic-mod-only flag,
and an icon RGBA color.

Three presets:
  --gen-gch        4 standard server channels (LookingForGroup,
                   World, Trade auto-join Stormwind, General)
  --gen-gch-rp     4 RP channels (RP_OOC public, RP_IC moderated
                   200-cap, RP_Forum invite-only 50-cap, RP_Events
                   password-protected)
  --gen-gch-admin  3 moderator-only channels (GMTraffic, AuditLog,
                   Backstage — all password-gated)

Validator catches: id+name required, channelKind/accessKind
range, duplicate channelIds, duplicate channel names (which
would route /join ambiguously), AutoJoinOnZone with
zoneDefaultMapId=0 (auto-join trigger would never fire). Warns
on dead zoneDefaultMapId set with non-AutoJoin kind.

Format count 123 -> 124. CLI flag count 1290 -> 1317.

tools/editor/cli_arg_required.cpp

@@ -380,6 +380,8 @@ const char* const kArgRequired[] = {
     "--gen-lan", "--gen-lan-quest", "--gen-lan-tooltip",
     "--info-wlan", "--validate-wlan",
     "--export-wlan-json", "--import-wlan-json",
+    "--gen-gch", "--gen-gch-rp", "--gen-gch-admin",
+    "--info-wgch", "--validate-wgch",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",