Implement in-process multi-dataset sync isolation across core, network, persistence, and tests

docs/persistence-providers.md

@@ -221,6 +221,14 @@ services.AddCBDDCCore()
     });
 ```
 
+### Multi-Dataset Partitioning
+
+Surreal persistence now stores `datasetId` on oplog, metadata, snapshot metadata, confirmation, and CDC checkpoint records.
+
+- Composite indexes include `datasetId` to prevent cross-dataset reads.
+- Legacy rows missing `datasetId` are interpreted as `primary` during reads.
+- Dataset-scoped store APIs (`ExportAsync(datasetId)`, `GetOplogAfterAsync(..., datasetId, ...)`) enforce isolation.
+
 ### CDC Durability Notes
 
 1. **Checkpoint semantics**: each consumer id has an independent durable cursor (`timestamp + hash`).