fix: remove unnecessary error wrapping (gptscript-ai#961)

Signed-off-by: Grant Linville <grant@acorn.io>

Author: g-linville

pkg/runner/runner.go

@@ -853,7 +853,7 @@ func (r *Runner) handleCredentials(callCtx engine.Context, monitor Monitor, env
 
 			res, err := r.subCall(callCtx.Ctx, callCtx, monitor, env, ref.ToolID, input, "", engine.CredentialToolCategory)
 			if err != nil {
-				return nil, fmt.Errorf("failed to run credential tool %s: %w", ref.Reference, err)
+				return nil, err
 			}
 
 			if res.Result == nil {

pkg/sdkserver/run.go

@@ -80,7 +80,7 @@ func processEventStreamOutput(logger mvl.Logger, w http.ResponseWriter, id strin
 		})
 	case err := <-errChan:
 		writeServerSentEvent(logger, w, map[string]any{
-			"stderr": fmt.Sprintf("failed to run: %v", err),
+			"stderr": err.Error(),
 		})
 	}