`create_mcp_server` promised one database and accepted a scope covering a set,
where the write tools exist and fail on use. It refuses that now.
Resolving is the public factory's job, as it is `HaikuRAG`'s: `_covering` takes
a scope someone already resolved, so the configured name survives without a
`DatabaseScope` reaching the public signature.
The test that a scope decides the database asserted `all(...)` over a search
that could return nothing, which held whatever the server read. It reads the
listing instead, so alpha's documents being present and beta's absent both have
to be true.
5f795cb0cb