feat(pipeline): add WBGD (Wowee Battleground Definition) format

Novel open replacement for Blizzard's BattlemasterList.dbc +
PvpDifficulty.dbc + the AzerothCore-style
battleground_template SQL tables. The 33rd open format
added to the editor.

Defines per-BG gameplay rules: player count brackets,
score-to-win, time limit, objective type (annihilation /
capture flag / control nodes / king of hill / resource race
/ carry object), per-team start positions, respawn timer,
and the WTKN currency token awarded on win.

Cross-references with previously-added formats:
  WBGD.entry.mapId       -> WMS.map.mapId
                            (where mapType=Battleground)
  WBGD.entry.markTokenId -> WTKN.entry.tokenId
                            (Mark of Honor for that BG)

The classic preset's markTokenId fields (102/103/104)
deliberately match WTKN.makePvp's "Mark of Honor: Warsong
Gulch / Arathi Basin / Alterac Valley" token ids — so the
demo content stack already wires together: WBGD.scoreToWin
reached → grant WTKN mark → which a vendor in WTRN can
charge in via item.extendedCost.

Format:
  • magic "WBGD", version 1, little-endian
  • per BG: battlegroundId / mapId / name / description /
    objectiveKind / min+maxPlayersPerSide /
    minLevel..maxLevel / scoreToWin / timeLimitSeconds /
    bracketSize / allianceStart vec3 + facing /
    hordeStart vec3 + facing / respawnTimeSeconds /
    markTokenId

Enums:
  • ObjectiveKind (6): Annihilation / CaptureFlag /
                       ControlNodes / KingOfHill /
                       ResourceRace / CarryObject

API: WoweeBattlegroundLoader::save / load / exists /
findById.

Three preset emitters showcase typical BG shapes:
  • makeStarter — 1 king-of-hill BG (10v10, 3-cap to win)
  • makeClassic — 3 classic BGs with authentic player
                   counts, level brackets, scoring, and
                   WTKN cross-refs (Warsong Gulch CTF /
                   Arathi Basin nodes / Alterac Valley
                   resource race)
  • makeArena   — 3 arena formats (Nagrand 2v2 / Blade's
                   Edge 3v3 / Lordaeron 5v5) — annihilation
                   objective + no respawn + 25 min cap

CLI added (5 flags, 628 documented total now):
  --gen-bg / --gen-bg-classic / --gen-bg-arena
  --info-wbgd / --validate-wbgd

Validator catches: bgId=0 + duplicates, empty name, unknown
objectiveKind, player count=0, min>max counts/levels,
scoreToWin=0 (no win condition), non-annihilation BG with
respawnTimeSeconds=0 (losing side cannot recover).

tools/editor/cli_arg_required.cpp

@@ -94,6 +94,8 @@ const char* const kArgRequired[] = {
     "--export-wsea-json", "--import-wsea-json",
     "--gen-mounts", "--gen-mounts-racial", "--gen-mounts-flying",
     "--info-wmou", "--validate-wmou",
+    "--gen-bg", "--gen-bg-classic", "--gen-bg-arena",
+    "--info-wbgd", "--validate-wbgd",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",