Fix ERP lager MCP schema properties

scripts/tests/erp_lager_mcp_tools_list_test.php

@@ -20,4 +20,5 @@ assert_test($names === ['erp_lager.list_products', 'erp_lager.get_product'], 'Un
 $productTool = $tools[1];
 assert_test($productTool['inputSchema']['required'] === ['product_id'], 'Product detail tool must require product_id');
 assert_test($productTool['inputSchema']['properties']['product_id']['type'] === 'integer', 'Product ID must be an integer');
+assert_test(is_object($tools[0]['inputSchema']['properties']), 'List products properties must serialize as a JSON object');
 fwrite(STDOUT, "erp_lager_mcp_tools_list_test: OK\n");