Add DuckDB support

[guillesd]

Hey! I think it would be great if you add DuckDB to the supported connectors. It should be very similar to implementing SQLlite with the nodejs client https://duckdb.org/docs/stable/clients/node_neo/overview.

Thanks for the project!

[tianzhou]

Haven't thought about supporting OLAP (not against it either)

[marr75]

Second this! In fact, beyond supporting projects that already use DDB, single file databases could unlock some really robust use cases where you ask the agent to persist structured results between runs.