gen_server: TimerHandle arm_after/cancel + Sys::Timer dispatch (RFC 015 §4.3, §5)

src/scheduler.rs

@@ -443,9 +443,6 @@ pub fn send_after_named<M: Send + 'static>(
 /// send onto a channel whose receiver is gone is dropped, exactly as a failed
 /// address resolve is (Erlang `send_after` semantics). `pid` is informational
 /// (who armed it); delivery lives entirely in the thunk.
-// Wired into `TimerHandle::arm_after` in the RFC 015 timer chunk; until then it
-// is referenced only from tests, so the non-test build would flag it dead.
-#[allow(dead_code)]
 pub(crate) fn send_after_to<T: Send + 'static>(
     after: std::time::Duration,
     tx: Sender<T>,