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/editor_brush.hpp

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <glm/glm.hpp>
+
+namespace wowee {
+namespace editor {
+
+enum class BrushMode {
+    Raise,
+    Lower,
+    Smooth,
+    Flatten,
+    Level
+};
+
+struct BrushSettings {
+    BrushMode mode = BrushMode::Raise;
+    float radius = 30.0f;
+    float strength = 5.0f;
+    float falloff = 0.5f;   // 0 = hard edge, 1 = full falloff
+    float flattenHeight = 0.0f;
+};
+
+class EditorBrush {
+public:
+    BrushSettings& settings() { return settings_; }
+    const BrushSettings& settings() const { return settings_; }
+
+    bool isActive() const { return active_; }
+    void setActive(bool a) { active_ = a; }
+
+    const glm::vec3& getPosition() const { return worldPos_; }
+    void setPosition(const glm::vec3& pos) { worldPos_ = pos; }
+
+    float getInfluence(float distance) const;
+
+private:
+    BrushSettings settings_;
+    glm::vec3 worldPos_{0.0f};
+    bool active_ = false;
+};
+
+} // namespace editor
+} // namespace wowee