fix(test): correct QuickCheck identifier generator validation

The test was using arbitrary String instance instead of the specific
genValidIdentifier generator, causing failures on invalid identifiers
like spaces. Now uses the proper generator for accurate validation.

test/Test/Language/Javascript/GeneratorsTest.hs

@@ -40,8 +40,9 @@ testGenerators = describe "QuickCheck Generators" $ do
     it "generates valid JSAST instances" $ property $
       \ast -> isValidJSAST (ast :: JSAST)
 
-    it "generates valid identifier strings" $ property $ \(ident :: String) ->
-      not (null ident) ==> all (`elem` (['a'..'z'] ++ ['A'..'Z'] ++ ['0'..'9'] ++ "_$")) ident
+    it "generates valid identifier strings" $ property $ do
+      ident <- genValidIdentifier
+      return $ not (null ident) && all (`elem` (['a'..'z'] ++ ['A'..'Z'] ++ ['0'..'9'] ++ "_$")) ident
 
   describe "Complex structure generators" $ do
     it "generates JSObjectProperty instances" $ property $