feat(editor): add standalone world editor (rough/WIP)

Standalone wowee_editor tool for creating custom WoW zones.
This is a rough initial implementation — many features work but
M2/WMO rendering still has issues (frame sync, texture layout
transitions) and needs further polish.

Terrain:
- Create new blank terrain with 10 biome types (Grassland, Forest,
  Jungle, Desert, Barrens, Snow, Swamp, Rocky, Beach, Volcanic)
- Load existing ADT tiles from extracted game data
- Sculpt brushes: Raise, Lower, Smooth, Flatten, Level
- Chunk edge stitching prevents seams between tiles
- Undo/redo (100-deep stack, Ctrl+Z/Ctrl+Shift+Z)
- Save to WoW ADT/WDT format

Texture Painting:
- Paint/Erase/Replace Base modes
- Full tileset texture browser (1285 textures from manifest)
- Per-zone directory filtering and search
- Alpha map editing with 4-layer limit (auto-replaces weakest)

Object Placement:
- M2 and WMO model placement with full manifest browser (11k M2s, 2k WMOs)
- M2Renderer + WMORenderer integrated (loads .skin files for WotLK)
- Ghost preview follows cursor before placing
- Ctrl+click selection, right-click context menu
- Transform gizmo (Move/Rotate/Scale with axis constraints)
- Position/rotation/scale editing in properties panel

NPC/Monster System:
- 631 creature presets scanned from manifest, categorized
  (Critters, Beasts, Humanoids, Undead, Demons, etc.)
- Stats editor: level, health, mana, damage, armor, faction
- Behavior: Stationary, Patrol, Wander, Scripted
- Aggro/leash radius, respawn time, flags (hostile/vendor/etc.)
- Save creature spawns to JSON

Water:
- Place water at configurable height per chunk
- Liquid types: Water, Ocean, Magma, Slime
- Rendered as translucent colored quads
- Saved in ADT MH2O format

Infrastructure:
- Free-fly camera (WASD/QE, right-drag look, scroll speed)
- 5-mode toolbar: Sculpt | Paint | Objects | Water | NPCs
- Asset browser indexes full manifest on startup
- Editor water/marker shaders (pos+color vertex format)
- forceNoCull added to M2Renderer for editor use
- AssetManifest::getEntries() and AssetManager::getManifest() exposed

Known issues:
- M2/WMO rendering may not display on first placement (frame index
  sync between update/render was misaligned — now fixed but untested
  end-to-end)
- Validation layer errors on shutdown (resource cleanup ordering)
- Object placement on steep terrain can miss raycast
- No undo for texture painting or object placement yet

tools/editor/terrain_editor.hpp

@@ -0,0 +1,83 @@
+#pragma once
+
+#include "editor_brush.hpp"
+#include "editor_history.hpp"
+#include "terrain_biomes.hpp"
+#include "pipeline/adt_loader.hpp"
+#include "pipeline/terrain_mesh.hpp"
+#include "rendering/camera.hpp"
+#include <vector>
+#include <functional>
+
+namespace wowee {
+namespace editor {
+
+class TerrainEditor {
+public:
+    TerrainEditor();
+
+    void setTerrain(pipeline::ADTTerrain* terrain) { terrain_ = terrain; }
+    pipeline::ADTTerrain* getTerrain() { return terrain_; }
+    const pipeline::ADTTerrain* getTerrain() const { return terrain_; }
+
+    EditorBrush& brush() { return brush_; }
+    const EditorBrush& brush() const { return brush_; }
+    EditorHistory& history() { return history_; }
+
+    static pipeline::ADTTerrain createBlankTerrain(int tileX, int tileY, float baseHeight = 100.0f,
+                                                     Biome biome = Biome::Grassland);
+
+    // Raycast against terrain, returns true if hit
+    bool raycastTerrain(const rendering::Ray& ray, glm::vec3& hitPos) const;
+
+    // Apply brush at current position (call per-frame while painting)
+    void applyBrush(float deltaTime);
+
+    // Begin/end a paint stroke (for undo grouping)
+    void beginStroke();
+    void endStroke();
+    bool isStrokeActive() const { return strokeActive_; }
+
+    // Get chunks modified since last call (for re-upload)
+    std::vector<int> consumeDirtyChunks();
+
+    // Regenerate mesh for specific chunks
+    pipeline::TerrainMesh regenerateMesh() const;
+    pipeline::ChunkMesh regenerateChunkMesh(int chunkIndex) const;
+
+    void undo();
+    void redo();
+
+    // Water editing
+    void setWaterLevel(const glm::vec3& center, float radius, float waterHeight, uint16_t liquidType = 0);
+    void removeWater(const glm::vec3& center, float radius);
+
+    bool hasUnsavedChanges() const { return dirty_; }
+    void markSaved() { dirty_ = false; }
+
+private:
+    void applyRaise(float dt);
+    void applySmooth(float dt);
+    void applyFlatten(float dt);
+    void stitchEdges(int chunkIdx);
+
+    std::vector<int> getAffectedChunks(const glm::vec3& center, float radius) const;
+    glm::vec3 chunkVertexWorldPos(int chunkIdx, int vertIdx) const;
+    float getVertexHeight(int chunkIdx, int vertIdx) const;
+    void setVertexHeight(int chunkIdx, int vertIdx, float height);
+
+    pipeline::ADTTerrain* terrain_ = nullptr;
+    EditorBrush brush_;
+    EditorHistory history_;
+
+    bool strokeActive_ = false;
+    bool dirty_ = false;
+    std::vector<int> dirtyChunks_;
+
+    static constexpr float TILE_SIZE = 533.33333f;
+    static constexpr float CHUNK_SIZE = TILE_SIZE / 16.0f;
+    static constexpr float GRID_STEP = CHUNK_SIZE / 8.0f;
+};
+
+} // namespace editor
+} // namespace wowee