Test: release Go-proxy RESTful contract tests verified passing in Go mode (#17468)

### Summary

Aligns Go and Python error codes/messages so both backends honor the
same RESTful API contract, removing implementation-specific error leaks
(MySQL errors, `ValueError`, `AttributeError`, Gin validator format) in
favor of clean business error codes.

**Chat list** — invalid `orderby` now returns code 101 (was: raw Python
`AttributeError` code 100); invalid `page`/`page_size` values fall back
to defaults (was: raw `ValueError`/`ProgrammingError` code 100).

**Dataset create/update/delete** — adds UUID validation (101),
extra-field rejection (101), duplicate-id detection (101), content-type
/ JSON-syntax / object-shape checks (101), and "lacks permission" for
nonexistent datasets (IDOR). Create auto-deduplicates dataset names.
Pagerank updates tolerate a missing ES index. List response includes
`parser_config` and `pagerank`.

**Session list/update** — adds filtering, sorting, and pagination
support. Empty payloads are valid no-ops. Authorization errors map to
code 109.

**Chunk list** — doc object uses Python key names (`chunk_count`,
`dataset_id`, `chunk_method`, run text status). Add validates list
element types.

**Document update** — adds `chunk_method` alias, pydantic-style Field
error messages, metadata index auto-create with refresh, and "These
documents do not belong to dataset" messages. List validates
`metadata_condition` and reports ownership errors for unmatched name/id
filters.

**Search completion** — `kb_ids` ownership failure returns code 102
instead of 109.

Released 31 contract tests from `GO_ONLY_SKIPS` (all verified passing on
both Go and Python backends with real LLM keys).

internal/service/document/document_parse.go

@@ -257,6 +257,15 @@ func (s *DocumentService) StopParseDocuments(ctx context.Context, datasetID stri
 
 	docs, err := s.validateDocsInDataset(ctx, deduped, datasetID)
 	if err != nil {
+		// Mirror the Python parse/stop endpoint's "Documents not found" message.
+		var notInDataset *documentsNotInDatasetError
+		if errors.As(err, &notInDataset) {
+			quoted := make([]string, len(notInDataset.ids))
+			for i, id := range notInDataset.ids {
+				quoted[i] = "'" + id + "'"
+			}
+			return nil, fmt.Errorf("Documents not found: [%s]", strings.Join(quoted, ", "))
+		}
 		return nil, err
 	}
 
@@ -277,6 +286,18 @@ func (s *DocumentService) StopParseDocuments(ctx context.Context, datasetID stri
 	return result, nil
 }
 
+// documentsNotInDatasetError carries the ids that are missing from (or do not
+// belong to) a dataset so each endpoint can format its own contract message.
+type documentsNotInDatasetError struct {
+	datasetID string
+	ids       []string
+}
+
+// Error mirrors the Python delete endpoint's message.
+func (e *documentsNotInDatasetError) Error() string {
+	return fmt.Sprintf("These documents do not belong to dataset %s or Document not found: %s", e.datasetID, strings.Join(e.ids, ", "))
+}
+
 // validateDocsInDataset deduplicates IDs, fetches the documents, and ensures
 // every document exists and belongs to the given dataset. Returns the resolved
 // documents.
@@ -285,17 +306,26 @@ func (s *DocumentService) validateDocsInDataset(ctx context.Context, docIDs []st
 	if err != nil {
 		return nil, fmt.Errorf("failed to fetch documents: %w", err)
 	}
+	invalid := make([]string, 0)
 	if len(docs) != len(docIDs) {
-		return nil, fmt.Errorf("some document IDs not found in dataset %s", datasetID)
-	}
-	var invalid []string
-	for _, d := range docs {
-		if d.KbID != datasetID {
-			invalid = append(invalid, d.ID)
+		found := make(map[string]struct{}, len(docs))
+		for _, d := range docs {
+			found[d.ID] = struct{}{}
+		}
+		for _, id := range docIDs {
+			if _, ok := found[id]; !ok {
+				invalid = append(invalid, id)
+			}
+		}
+	} else {
+		for _, d := range docs {
+			if d.KbID != datasetID {
+				invalid = append(invalid, d.ID)
+			}
 		}
 	}
 	if len(invalid) > 0 {
-		return nil, fmt.Errorf("These documents do not belong to dataset %s: %v", datasetID, invalid)
+		return nil, &documentsNotInDatasetError{datasetID: datasetID, ids: invalid}
 	}
 	return docs, nil
 }