mobilitydb-indexes-duckdb-bridge-dynlink

Phase A dynlink-mode duckdb bridge for mobilitydb_indexes (target mobilitydb_indexes).

The bridge imports only compose:dynlink/linker and dispatches SQL scalar arms as CBOR envelopes through the resident provider mobilitydb_indexes-composed. Aggregate / cast / table / pragma / column paths return duckerror::unsupported at Phase A scope.