Named supervisor for pipeline tiers with dispatch: :task.

What problem this solves

Some descended tiers should run asynchronously without a hard concurrency cap. :task dispatch lazily starts one TierSession per tier per owner under this supervisor (unbounded by default via :max_children :infinity).

Internal note

Thin wrapper around TierSupervisor registered as TierSupervisor.Task.

RFCs

• No STUN/TURN RFC; OTP supervision for async tier workers