Internal refactor

[vseventer]

• Refactor CLI execution to use a per-invocation command queue while preserving chained command order and global option handling.
• File and stream conversions now inspect input metadata before draining queued operations and pass { format, metadata } to command handlers. Format-specific output options are applied only to the selected format.
• The test suite has been migrated to the async Yargs API and expanded to cover chained commands, metadata context, format handling, stream errors, and local queue behavior.