feat(orbit-local): scope orbit schema output by positional table names

closes #711 (closed)

What does this MR do and why?

orbit schema dumped every table with no way to scope the output. This adds optional positional table names as a filter — matching the glab orbit remote schema <Entity> mental model in the new DuckDB-backed local model.

orbit schema                          # all tables (unchanged)
orbit schema gl_definition            # scoped to one table
orbit schema gl_definition gl_edge    # scoped to two tables
orbit schema gl_definition --raw      # scoped, JSON output

Testing Built with --features duckdb-client/bundled and validated all four cases locally against an indexed graph. All return correct scoped output.