feat(woc): add WMO collision meshes to exported zone collision

WoweeCollision previously only contained terrain triangles; placed WMO
buildings had no collision in the exported zone, so players could walk
through walls. Added WoweeCollisionBuilder::addMesh() that transforms a
local-space mesh into world space with slope-based walkability flags,
and the editor's exportZone now walks every placed WMO and feeds each
group's geometry through it. Indoor vs outdoor groups are tagged via
the WMO group flag.

include/pipeline/wowee_collision.hpp

@@ -40,6 +40,16 @@ public:
     static WoweeCollision fromTerrain(const ADTTerrain& terrain,
                                        float steepAngle = 50.0f);
 
+    // Append a transformed mesh to an existing collision (for WMO/M2 instances).
+    // `vertices` are local-space; `transform` puts them into world space.
+    // Triangles are classified by slope using `steepAngle`.
+    static void addMesh(WoweeCollision& collision,
+                        const std::vector<glm::vec3>& vertices,
+                        const std::vector<uint32_t>& indices,
+                        const glm::mat4& transform,
+                        uint8_t extraFlags = 0,
+                        float steepAngle = 50.0f);
+
     // Save collision mesh to binary file
     static bool save(const WoweeCollision& collision, const std::string& path);