D4InterpretedProxy class abstract

Marker for native objects produced by an interface-proxy factory that wrap an InterpretedInstance.

Why this exists: When a script subclasses a bridged type whose downstream native API (e.g., RenderObject.parentData = _MyParentData()) requires a native instance, a runtime registration produces a _InterpretedX proxy that satisfies the native is-check. The original InterpretedInstance is cached on the proxy.

On the way back, the script may cast that proxy to its scripted subtype (e.g., child.parentData! as _MyParentData) and access user-defined fields/methods on it. Without unwrap support the cast returns the bridged proxy, and field access fails because the bridge knows nothing about the scripted members.

Proxies that hold a back-reference to an interpreted instance should implement this marker. visitAsExpression checks for it and unwraps to d4rtInstance when the cast target name matches a class/mixin/ interface in the instance's class chain.