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_history.cpp

@@ -0,0 +1,83 @@
+#include "editor_history.hpp"
+
+namespace wowee {
+namespace editor {
+
+void EditorHistory::beginEdit(const pipeline::ADTTerrain& terrain,
+                               const std::vector<int>& affectedChunks) {
+    pending_ = {};
+    pending_.before.reserve(affectedChunks.size());
+    for (int idx : affectedChunks) {
+        ChunkSnapshot snap;
+        snap.chunkIndex = idx;
+        snap.heights = terrain.chunks[idx].heightMap.heights;
+        pending_.before.push_back(snap);
+    }
+}
+
+void EditorHistory::endEdit(const pipeline::ADTTerrain& terrain) {
+    pending_.after.reserve(pending_.before.size());
+    lastAffected_.clear();
+    for (const auto& snap : pending_.before) {
+        ChunkSnapshot after;
+        after.chunkIndex = snap.chunkIndex;
+        after.heights = terrain.chunks[snap.chunkIndex].heightMap.heights;
+        pending_.after.push_back(after);
+        lastAffected_.push_back(snap.chunkIndex);
+    }
+
+    // Only push if something actually changed
+    bool changed = false;
+    for (size_t i = 0; i < pending_.before.size(); i++) {
+        if (pending_.before[i].heights != pending_.after[i].heights) {
+            changed = true;
+            break;
+        }
+    }
+    if (!changed) return;
+
+    undoStack_.push_back(std::move(pending_));
+    redoStack_.clear();
+
+    if (undoStack_.size() > MAX_UNDO)
+        undoStack_.erase(undoStack_.begin());
+}
+
+void EditorHistory::undo(pipeline::ADTTerrain& terrain) {
+    if (undoStack_.empty()) return;
+
+    auto cmd = std::move(undoStack_.back());
+    undoStack_.pop_back();
+
+    lastAffected_.clear();
+    for (const auto& snap : cmd.before) {
+        terrain.chunks[snap.chunkIndex].heightMap.heights = snap.heights;
+        lastAffected_.push_back(snap.chunkIndex);
+    }
+
+    redoStack_.push_back(std::move(cmd));
+}
+
+void EditorHistory::redo(pipeline::ADTTerrain& terrain) {
+    if (redoStack_.empty()) return;
+
+    auto cmd = std::move(redoStack_.back());
+    redoStack_.pop_back();
+
+    lastAffected_.clear();
+    for (const auto& snap : cmd.after) {
+        terrain.chunks[snap.chunkIndex].heightMap.heights = snap.heights;
+        lastAffected_.push_back(snap.chunkIndex);
+    }
+
+    undoStack_.push_back(std::move(cmd));
+}
+
+void EditorHistory::clear() {
+    undoStack_.clear();
+    redoStack_.clear();
+    lastAffected_.clear();
+}
+
+} // namespace editor
+} // namespace wowee