A name nothing covers raised `KeyError` in four places and
`AmbiguousDatabaseError` in a fifth, so a caller had to catch both and neither
name said what happened. `UnknownDatabaseError` is all of them, exported from
`haiku.rag.store` beside the other errors.
It subclasses `KeyError`, since selecting by name is a lookup, and prints its
message plainly rather than quoted as a missing key. Both CLIs turn it into the
same clean exit they already gave the others.
Closes#582. `lancedb.databases` entries already classify a location by
whether it carries a scheme; `lancedb.uri` was taken as a URI whatever it
said, so a local path was opened as object storage and a mistyped one
became a new empty database instead of failing. Both settings now place a
database the same way, and `--db PATH` overrides either.
The CLI decides only what it knows — that --db and --database are the same
thing said twice, and whether a command reads more than one — and hands the
resolved scope down. Nothing rewrites the configuration, so a named database
keeps the name results and citations carry, and a remote one opens the URI
it was configured with rather than the local path standing in for it.
HaikuRAGApp, ChatApp and InspectorApp take that scope and nothing else.
Selection reaches the client through a private constructor, so the public
signature still takes a path or names.
FederatedSession opens the databases a query covers and owns their
teardown; the client keeps the wrappers it hands out. A wrapper releases
what it built and never closes the database it borrowed.
DatabaseScope.resolve reads configuration and at most one selector; a
DatabaseRef carries the configured name and a location already resolved to
a URI or a path, so a path a caller names is never reinterpreted. Nothing
consumes it yet.
