Macro ic_memory 

macro_rules! ic_memory {
    ($label:path, $id:expr) => { ... };
}

Declare a stable-memory slot backed by the Canic memory registry.

The macro enqueues a registration for later validation (during init_eager_tls) and immediately returns the VirtualMemory handle so callers can wrap it in Cell, BTreeMap, and other structures. Memory IDs are automatically namespaced per crate via CARGO_PKG_NAME.