`resolve_db_path` manufactured the default path whenever `lancedb.databases`
was empty, and `covers_several_databases` read coverage back out of the
configuration, so a capability built without a client opened
`storage.data_dir/haiku.rag.lancedb` instead of what `lancedb.uri` placed.
The entry point resolves a `DatabaseScope` instead: instructions ask it what
it covers and `_ensure_rag` opens it through `HaikuRAG._covering`, so
coverage is decided once rather than encoded in a path and re-derived.
`Sandbox._covering` takes the scope the capability already resolved, beside
the public constructor that takes a path. The factory signatures are
unchanged.
71e4e4a40a