Constant META_KEY_SCOPE 

pub const META_KEY_SCOPE: &str = "scope";

metadata.scope — visibility marker (one of [MemoryScope::all_strs] at crate::models::namespace::MemoryScope). Controls which agents can see a memory via hierarchical namespace matching per Task 1.5. Memories without this key are treated as "private" by the query layer (see crate::models::namespace::MemoryScope::default()).