Function merge_meta_patch 

fn merge_meta_patch(meta: &mut HashMap<String, Value>, patch: &Value) -> bool

Phase E.5.3 — shallow merge a JSON object patch into a MetaMapType. Mirrors backend::obj::merge_meta semantics so UpdateObjectMeta keeps behaving the same way after the reducer migration:

• Keys ending in :* with a true value clear all keys with that prefix (e.g. {"term:*": true} removes every term* key) before regular merging.
• null patch values delete the corresponding key.
• Other values replace the key. Returns true if anything actually changed.