Read one or more Metabase resources via metabase:// URI patterns.

Calls the read_resource tool in metabase.metabot.tools.resources — the same record the agent loop calls, so URI dispatch, per-URI permission checks and the per-URI failure text are shared. A URI that cannot be read becomes that item's :error; the call still returns 200 with the items that did read. Each request accepts up to five URIs; oversized batches return 400 before any reads.