fix: add missing error.param field to chat error responses

Author: jpr5

src/helpers.ts

@@ -172,6 +172,7 @@ export function serializeErrorResponse(response: ErrorResponse): string {
     error: {
       message: response.error.message,
       type: response.error.type ?? "server_error",
+      param: response.error.param ?? null,
       code: response.error.code ?? null,
     },
   });

src/types.ts

@@ -165,7 +165,7 @@ export interface ContentWithToolCallsResponse extends ResponseOverrides {
 }
 
 export interface ErrorResponse {
-  error: { message: string; type?: string; code?: string };
+  error: { message: string; type?: string; param?: string | null; code?: string };
   status?: number;
 }