Fix character attachment to follow mount's full rotation

Character now properly rotates with the mount during flight instead of just
bobbing up and down. This fixes the issue where the character appeared to
float away from the mount during rolls and pitch changes.

Implementation:
- Create rotation matrix from mount's pitch, roll, yaw
- Transform rider offset through rotation (local → world space)
- Apply same rotation to character model (glued to mount)
- Character stays properly seated during all mount movements

Before: Character only offset vertically, sliding around during banking
After: Character rotates with mount, stays firmly attached during all maneuvers

src/rendering/renderer.cpp

@@ -702,10 +702,28 @@ void Renderer::updateCharacterAnimation() {
             }
         }
 
-        // Offset player Z above mount + bob
-        glm::vec3 playerPos = characterPosition;
-        playerPos.z += mountHeightOffset_ + mountBob;
+        // Character follows mount's full rotation (pitch, roll, yaw)
+        // This keeps the character "glued" to the mount during banking/climbing
+        float yawRad = glm::radians(characterYaw);
+
+        // Create rotation matrix from mount's orientation
+        glm::mat4 mountRotation = glm::mat4(1.0f);
+        mountRotation = glm::rotate(mountRotation, yawRad, glm::vec3(0.0f, 0.0f, 1.0f));       // Yaw (Z)
+        mountRotation = glm::rotate(mountRotation, mountRoll_, glm::vec3(1.0f, 0.0f, 0.0f));   // Roll (X)
+        mountRotation = glm::rotate(mountRotation, mountPitch_, glm::vec3(0.0f, 1.0f, 0.0f));  // Pitch (Y)
+
+        // Offset in mount's local space (rider sits above mount)
+        glm::vec3 localOffset(0.0f, 0.0f, mountHeightOffset_ + mountBob);
+
+        // Transform offset through mount's rotation to get world-space offset
+        glm::vec3 worldOffset = glm::vec3(mountRotation * glm::vec4(localOffset, 0.0f));
+
+        // Character position = mount position + rotated offset
+        glm::vec3 playerPos = characterPosition + worldOffset;
         characterRenderer->setInstancePosition(characterInstanceId, playerPos);
+
+        // Character rotates with mount (same pitch, roll, yaw)
+        characterRenderer->setInstanceRotation(characterInstanceId, glm::vec3(mountPitch_, mountRoll_, yawRad));
         return;
     }