Batch 37: #1471's test mosaic sets #1176's lens_metadata

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/merge/src/frame.rs

@@ -308,6 +308,7 @@ mod tests {
             wb_multipliers,
             linearized: false,
             opcodes: OpcodeLists::default(),
+            lens_metadata: Default::default(),
             metadata: Metadata::default(),
         }
     }