fix(evidence): isolate vectors by workspace

harness/tht/search/evidence.py

@@ -30,7 +30,8 @@ class ActiveEvidenceSearcher:
                 hits.extend(self.delegate.search(embedding, **kwargs))
             if include_evidence:
                 manifest = self.corpus.active_manifest()
-                if manifest is not None:
+                workspace_id = manifest.metadata.get("workspace_id") if manifest else None
+                if manifest is not None and isinstance(workspace_id, str):
                     by_generation: dict[str, list[str]] = {}
                     mapping = dict(manifest.metadata.get("document_generations", {}))
                     for document in manifest.documents:
@@ -43,6 +44,7 @@ class ActiveEvidenceSearcher:
                             metadata_filter={
                                 "vector_generation": generation,
                                 "document_ids": sorted(document_ids),
+                                "workspace_id": workspace_id,
                             },
                         ))
         return sorted(hits, key=lambda hit: (-hit.similarity, hit.id))[:top_n]