Give the CEM sprite test's MobData the emissive field

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/horizon-client/src/mobs/cem.rs

@@ -892,6 +892,7 @@ mod tests {
             villager_hats: Default::default(),
             cem: std::sync::RwLock::new(models.clone()),
             random_textures: Default::default(),
+            emissive: Default::default(),
             pois: Default::default(),
             species_placements: Default::default(),
         };