feat(pipeline): add WTRN (Wowee Trainer / Vendor catalog) format

Novel open replacement for AzerothCore-style npc_trainer +
npc_vendor SQL tables PLUS the Blizzard TrainerSpells.dbc
family. The 22nd open format added to the editor.

Unifies trainer spell lists and vendor item inventories
into one per-NPC entry. A creature flagged Trainer or
Vendor in WCRT references a WTRN entry that lists what they
teach / sell. The same NPC can be both — kindMask is a
bitmask covering the Trainer (0x01) and Vendor (0x02) kinds.

This format closes a major cross-format gap: WCRT.npcFlags
already had Vendor / Trainer bits, but until now there was
no format defining what a vendor sells or what a trainer
teaches. Now an NPC marked Vendor in WCRT has a real
inventory, and an NPC marked Trainer has a real spell list.

Cross-references — every WTRN field has a real format target:
  WTRN.entry.npcId           -> WCRT.entry.creatureId
  WTRN.spell.spellId         -> WSPL.entry.spellId
  WTRN.spell.requiredSkillId -> WSKL.entry.skillId
  WTRN.item.itemId           -> WIT.entry.itemId

Format:
  • magic "WTRN", version 1, little-endian
  • per NPC: npcId / kindMask / greeting + spells[] + items[]
  • per spell offer: spellId / moneyCostCopper /
    requiredSkillId / requiredSkillRank / requiredLevel
  • per item offer: itemId / stockCount (0xFFFFFFFF =
    unlimited) / restockSec / extendedCost / moneyCostCopper
    (0 = inherit from WIT.buyPrice)

API: WoweeTrainerLoader::save / load / exists / findByNpc;
presets makeStarter (innkeeper 4001 as both trainer +
vendor: teaches First Aid + sells starter items),
makeMageTrainer (NPC 4003 teaches the WSPL mage spells
at scaling cost), makeWeaponVendor (NPC 4002 sells WIT
weapons with mixed unlimited/finite stock + restock timers).

CLI added (5 flags, 551 documented total now):
  --gen-trainers / --gen-trainers-mage / --gen-trainers-weapons
  --info-wtrn / --validate-wtrn

Validator catches: npcId=0 + duplicates, kindMask=0 (NPC
offers nothing), Trainer flag without spells, Vendor flag
without items, spells/items present without the matching
kind bit (silently ignored at runtime), spellId=0 / itemId=0
in offers, finite stock with restockSec=0 (single-fill —
usually intentional but worth surfacing).

The 3 presets deliberately use npcIds matching WCRT village
merchants (4001/4002/4003) so the demo content stack is
self-consistent: WCRT 4001 has the Vendor + Trainer flag,
and WTRN 4001 actually defines what they sell and teach.

include/pipeline/wowee_trainers.hpp

@@ -0,0 +1,120 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace wowee {
+namespace pipeline {
+
+// Wowee Open Trainer / Vendor catalog (.wtrn) — novel
+// replacement for AzerothCore-style npc_trainer + npc_vendor
+// SQL tables PLUS the Blizzard TrainerSpells.dbc family.
+// The 22nd open format added to the editor.
+//
+// Unifies trainer spell lists and vendor inventories into one
+// per-NPC entry. A creature flagged Trainer or Vendor in WCRT
+// references a WTRN entry that lists what they teach / sell.
+// The same NPC can be both — kindMask is a bitmask covering
+// the Trainer (0x01) and Vendor (0x02) kinds.
+//
+// Cross-references with previously-added formats:
+//   WTRN.entry.npcId            → WCRT.entry.creatureId
+//   WTRN.spell.spellId          → WSPL.entry.spellId
+//   WTRN.spell.requiredSkillId  → WSKL.entry.skillId
+//   WTRN.item.itemId            → WIT.entry.itemId
+//
+// Binary layout (little-endian):
+//   magic[4]            = "WTRN"
+//   version (uint32)    = current 1
+//   nameLen + name (catalog label)
+//   entryCount (uint32)
+//   entries (each):
+//     npcId (uint32)
+//     kindMask (uint8) + pad[3]
+//     greetingLen + greeting
+//     spellCount (uint16) + itemCount (uint16)
+//     spells (spellCount × {
+//       spellId (uint32)
+//       moneyCostCopper (uint32)
+//       requiredSkillId (uint32)
+//       requiredSkillRank (uint16)
+//       requiredLevel (uint16)
+//     })
+//     items (itemCount × {
+//       itemId (uint32)
+//       stockCount (uint32)        -- 0xFFFFFFFF = unlimited
+//       restockSec (uint32)
+//       extendedCost (uint32)
+//       moneyCostCopper (uint32)   -- 0 = use WIT.buyPrice
+//     })
+struct WoweeTrainer {
+    enum KindMask : uint8_t {
+        Trainer = 0x01,
+        Vendor  = 0x02,
+    };
+
+    static constexpr uint32_t kUnlimitedStock = 0xFFFFFFFFu;
+
+    struct SpellOffer {
+        uint32_t spellId = 0;
+        uint32_t moneyCostCopper = 0;
+        uint32_t requiredSkillId = 0;        // 0 = no skill prerequisite
+        uint16_t requiredSkillRank = 0;
+        uint16_t requiredLevel = 1;
+    };
+
+    struct ItemOffer {
+        uint32_t itemId = 0;
+        uint32_t stockCount = kUnlimitedStock;
+        uint32_t restockSec = 0;
+        uint32_t extendedCost = 0;           // 0 = copper-only
+        uint32_t moneyCostCopper = 0;        // 0 = inherit from WIT
+    };
+
+    struct Entry {
+        uint32_t npcId = 0;
+        uint8_t kindMask = 0;
+        std::string greeting;
+        std::vector<SpellOffer> spells;
+        std::vector<ItemOffer> items;
+    };
+
+    std::string name;
+    std::vector<Entry> entries;
+
+    bool isValid() const { return !entries.empty(); }
+
+    // Lookup by npcId — nullptr if not present.
+    const Entry* findByNpc(uint32_t npcId) const;
+
+    // Decode the kindMask into a short string (e.g.
+    // "trainer+vendor" or just "vendor").
+    static std::string kindMaskName(uint8_t k);
+};
+
+class WoweeTrainerLoader {
+public:
+    static bool save(const WoweeTrainer& cat,
+                     const std::string& basePath);
+    static WoweeTrainer load(const std::string& basePath);
+    static bool exists(const std::string& basePath);
+
+    // Preset emitters used by --gen-trainers* variants.
+    //
+    //   makeStarter — 1 NPC (Bartleby innkeeper, npcId=4001)
+    //                  acting as both vendor + trainer: sells
+    //                  3 starter items + teaches First Aid.
+    //   makeMageTrainer — npcId=4003 (alchemist) becomes a
+    //                      mage trainer offering Frostbolt /
+    //                      Fireball / Arcane Intellect / Blink
+    //                      at appropriate ranks.
+    //   makeWeaponVendor — npcId=4002 (smith) sells 5 weapons
+    //                       across the WIT weapon catalog.
+    static WoweeTrainer makeStarter(const std::string& catalogName);
+    static WoweeTrainer makeMageTrainer(const std::string& catalogName);
+    static WoweeTrainer makeWeaponVendor(const std::string& catalogName);
+};
+
+} // namespace pipeline
+} // namespace wowee