fix: Incompatible parseIsWeb detection prevents WASM support (#1096)

Author: Copilot

packages/dart/lib/src/base/parse_constants.dart

@@ -86,4 +86,4 @@ const String keyError = 'error';
 const String keyCode = 'code';
 const String keyNetworkError = 'NetworkError';
 
-const bool parseIsWeb = identical(0, 0.0);
+const bool parseIsWeb = bool.fromEnvironment('dart.library.js_util');