Sync Collection Schema

Sample documents from Qdrant and automatically discover new fields to add to the collection's output_schema.

This endpoint:
- Samples N documents from the collection (default: 1000)
- Discovers all fields present in actual documents
- Merges discovered fields into the collection's output_schema (additive only)
- Optionally cascades schema updates to downstream collections
- Respects debounce window (max once per 5 minutes, unless force=true)

The sync operation is additive only - it never removes or changes existing field types.

Use this endpoint to:
- Manually trigger schema discovery after data ingestion
- Force an immediate schema sync (bypassing debounce)
- Update schemas with new fields discovered in documents