Overview

$_documentResultsAndMetadata is a transport container that never executes directly. Before the pipeline runs it must be lowered into concrete execution stages. This parent ticket tracks the full standalone compilation workflow, broken into sub-tasks.

Background

For standalone (non-sharded) execution, lowering means replacing the container with an Exchange that routes the extension's tagged output stream to two consumers: document results unwrapped via \$replaceRoot(\$payload), and metadata consumed by \$setVariableFromSubPipeline to set $$SEARCH_META inline before any downstream stage reads it.

Acceptance Criteria

• All sub-tasks complete
• Standalone $search with $$SEARCH_META resolves correctly end-to-end
• $search inside $unionWith and $lookup sub-pipelines lowers correctly