`haiku-rag mcp` passes covers_set=True and _covering no longer refuses a
scope over several databases. search_documents, search_documents_by_image,
ask_question and analyze take `sources`; get_document takes `source`;
DocumentInfo carries `source`. format_citations gains include_source, which
ask_question sets from covers_multiple so citations name their database
only when the server covers several.
Refs #599
add_document_from_file, add_document_from_url, add_document_from_text
and delete_document are gone. create_mcp_server and _covering lose
read_only; the client always opens with read_only=True, so the
--read-only flag before `mcp` is redundant and the docs, Dockerfiles and
compose example drop it.
Ingestion is `haiku-rag add`/`add-src`/`delete` and haiku-ingester. No
known consumer used the write tools; one stdio server per client window
made multi-writer the accidental default, and streamable HTTP has no auth.
The test_app stub drops a comment and __init__ that described run_mcp
constructing the client positionally; every path goes through _covering.
Refs #599
