test(trait): add test case for trait class constant inheritance behavior

- Create test verifying trait class constants remain bound to composing class
- Add test with ClassIdentityTrait using __CLASS__ and self::class
- Include Base class that uses the trait and Child extending Base
- Verify magicClass() returns "Base" instead of "Child"
- Verify selfClass() returns "Base" instead of "Child"
- Add expected output showing correct binding behavior

tests/compiler/trait/trait-class-constant-inherited.phpt

@@ -0,0 +1,36 @@
+--TEST--
+Trait class constants remain bound to the composing class when inherited
+--FILE--
+<?php
+trait ClassIdentityTrait
+{
+    public function magicClass(): string
+    {
+        return __CLASS__;
+    }
+
+    public function selfClass(): string
+    {
+        return self::class;
+    }
+}
+
+class Base
+{
+    use ClassIdentityTrait;
+}
+
+class Child extends Base
+{
+}
+
+function main(): void
+{
+    $object = new Child();
+    var_dump($object->magicClass());
+    var_dump($object->selfClass());
+}
+?>
+--EXPECT--
+string(4) "Base"
+string(4) "Base"