Struct IdentityHandle 

pub struct IdentityHandle { /* private fields */ }

Opaque handle holding an ed25519 keypair plus a local TokenCache. Matches the PyO3 / NAPI Identity pyclass layout — cheap to clone (both fields are Arcs inside the core), and the cache is owned by the handle rather than shared across peers.

Same HandleGuard recipe as the cortex handles (see super::handle_guard for soundness). Box stays leaked across _free; inner Arcs live in ManuallyDrop so the free can take and drop them after quiescing in-flight ops.