pub static REQUEST_CT: LocalKey<CancellationToken>Expand description
#1781: the cancellation token of the request currently being served,
scoped by call_tool around the whole guarded dispatch.
A task-local rather than a field on the shared server: rmcp spawns one
task per request and hands each its own child_token, so concurrent
calls would otherwise overwrite one another’s token — and cancelling the
wrong command is worse than not cancelling at all.