`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.
`Agent.from_spec` raised `TypeError` on `RAGCapability` and `AnalysisCapability`,
whose constructors take a state class, packaged instruction text and a tool-name
set, and silently omitted both from the generated spec schema. The two
zero-configuration capabilities constructed but with `id=None`, so pydantic-ai's
duplicate-id rejection no longer held and a spec could register two citation
policies, defeating the single-decision-maker invariant.
Override `from_spec` on all four, delegating to `create_capability()` so ids and
instructions come from one place. The spec surface is `db_path`, `config`,
`defer_loading`, `request_limit` and `vision`; a live `HaikuRAG` client stays out
of it, and a `config` mapping is validated through `AppConfig`.
