1cd600f70f
* Add SourceManager to Engine struct * Update Engine methods to use the SourceManager * Fix GCS test The original was testing that `Init()` errors weren't surfaced in `Finish()`, but the `SourceManager` changed that behavior. * JobProgress race fixes * Add contextual values * Remove unused code * Add debug logs * Rename WithConcurrency to WithConcurrentSources * Always forward chunks to the output chunks channel