Feature Request: Support PhantomVar<T for storage-less properties with custom getters/setters

Feature Request: Support PhantomVar<T for storage-less properties with custom getters/setters: a task in LegoFlow-SWE (Harbor dataset). Currently, Godot-Rust requires that every field annotated with var or export stores a real value of the declared type. This makes it impossible to define…

The task

Currently, Godot-Rust requires that every field annotated with `#[var]` or `#[export]` stores a real value of the declared type. This makes it impossible to define **synthetic properties** — properties whose value is entirely computed by getter/setter methods and has no underlying storage. Examples include read-only…

Part of Lego-X/LegoFlow-SWE.