fix workbench runtime nullable json reads

internal/cloud/server-workbench-http.ts

@@ -1890,6 +1890,15 @@ function handleWorkbenchReadModelFailure(response, url, options = {}, error) {
 function classifyWorkbenchReadModelFailure(error) {
   const message = String(error?.message ?? error ?? "");
   const code = String(error?.code ?? "").toLowerCase();
+  const runtimeStatus = Number(error?.data?.status ?? 0);
+  const runtimePayloadError = error?.data?.payload?.error ?? null;
+  if (error?.name === "WorkbenchRuntimeDependencyError" || code.startsWith("workbench_runtime_")) {
+    return {
+      statusCode: Number.isFinite(runtimeStatus) && runtimeStatus >= 500 ? 503 : 500,
+      code: String(runtimePayloadError?.code ?? error?.code ?? "workbench_runtime_dependency_failed"),
+      message: String(runtimePayloadError?.message ?? error?.message ?? "Workbench runtime dependency failed.")
+    };
+  }
   if (/timeout|connection terminated|terminating connection|econnreset|econnrefused|etimedout/iu.test(message) || /timeout|econnreset|econnrefused|etimedout/u.test(code)) {
     return {
       statusCode: 503,

internal/workbenchruntime/service.go

@@ -480,12 +480,12 @@ func (s *Server) queryJSONColumn(ctx context.Context, sqlText string, args []any
 	defer rows.Close()
 	result := []any{}
 	for rows.Next() {
-		var raw []byte
+		var raw sql.NullString
 		if err := rows.Scan(&raw); err != nil {
 			return nil, err
 		}
 		var item any
-		if len(raw) > 0 && json.Unmarshal(raw, &item) == nil && item != nil {
+		if raw.Valid && strings.TrimSpace(raw.String) != "" && json.Unmarshal([]byte(raw.String), &item) == nil && item != nil {
 			result = append(result, item)
 		}
 	}
@@ -571,14 +571,14 @@ func (s *Server) readProjectionOutbox(ctx context.Context, query outboxQuery) ([
 		var outboxSeq, projectedSeq, sourceSeq sql.NullInt64
 		var traceID, sessionID, turnID, messageID, sourceEventID, commitType sql.NullString
 		var terminal, sealed sql.NullBool
-		var raw []byte
+		var raw sql.NullString
 		var createdAt sql.NullTime
 		if err := rows.Scan(&outboxSeq, &traceID, &sessionID, &turnID, &messageID, &projectedSeq, &sourceSeq, &sourceEventID, &commitType, &terminal, &sealed, &raw, &createdAt); err != nil {
 			return nil, err
 		}
 		var payload any
-		if len(raw) > 0 {
-			_ = json.Unmarshal(raw, &payload)
+		if raw.Valid && strings.TrimSpace(raw.String) != "" {
+			_ = json.Unmarshal([]byte(raw.String), &payload)
 		}
 		result = append(result, map[string]any{
 			"outboxSeq":     nullableInt(outboxSeq),