fix: handle text session summary timestamps

internal/workbenchruntime/service.go

@@ -518,9 +518,9 @@ func (s *Server) querySessionSummaries(ctx context.Context, stage string, sqlTex
 		defer rows.Close()
 		for rows.Next() {
 			var sessionID, ownerUserID, projectID, conversationID, threadID, status, lastTraceID, sourceEventID, sessionJSON sql.NullString
+			var createdAt, updatedAt sql.NullString
 			var projectedSeq, sourceSeq sql.NullInt64
 			var terminal, sealed sql.NullBool
-			var createdAt, updatedAt sql.NullTime
 			if err := rows.Scan(&sessionID, &ownerUserID, &projectID, &conversationID, &threadID, &status, &lastTraceID, &projectedSeq, &sourceSeq, &sourceEventID, &terminal, &sealed, &createdAt, &updatedAt, &sessionJSON); err != nil {
 				return err
 			}
@@ -541,8 +541,8 @@ func (s *Server) querySessionSummaries(ctx context.Context, stage string, sqlTex
 				"sourceEventId":  nullableString(sourceEventID),
 				"terminal":       nullableBool(terminal),
 				"sealed":         nullableBool(sealed),
-				"createdAt":      nullableTime(createdAt),
-				"updatedAt":      first(nullableTime(updatedAt), nullableTime(createdAt)),
+				"createdAt":      nullableTimeText(createdAt),
+				"updatedAt":      first(nullableTimeText(updatedAt), nullableTimeText(createdAt)),
 				"valuesPrinted":  false,
 				"valuesRedacted": true,
 			}
@@ -1336,6 +1336,21 @@ func nullableTime(value sql.NullTime) string {
 	return ""
 }
 
+func nullableTimeText(value sql.NullString) string {
+	if !value.Valid {
+		return ""
+	}
+	raw := strings.TrimSpace(value.String)
+	if raw == "" {
+		return ""
+	}
+	parsed, err := time.Parse(time.RFC3339Nano, raw)
+	if err == nil {
+		return parsed.UTC().Format(time.RFC3339Nano)
+	}
+	return raw
+}
+
 type sqlStateError interface{ SQLState() string }
 
 func sqlErrorCode(err error) string {