SQL builders for DuckDB extension management.

These helpers build INSTALL and LOAD statements while validating extension names as SQL identifiers. They return iodata so they can be passed directly to QuackDB.query/4, QuackDB.query!/4, or Repo.query/3.

alias QuackDB.Extension

QuackDB.query!(conn, Extension.install(:httpfs))
QuackDB.query!(conn, Extension.load(:httpfs))

QuackDB.SQL.install/1 and QuackDB.SQL.load/1 remain available as the lower-level generic SQL helpers.