handle_input() previously drained terminal events in an unbounded
while-poll loop, so a continuously-ready input stream could keep the
frontend inside handle_input() indefinitely, starving managed-event
processing, completion checks, peer-close stop policy, and rendering
in the outer run_tui() loop.
Bound each call to at most INPUT_EVENT_WORK_BUDGET (128) polled
terminal events, mirroring the MANAGED_EVENT_WORK_BUDGET pattern
already used for managed event draining. All polled events count
against the budget, including ignored/unknown/release events, so a
stream of non-actionable input can't bypass the bound. Remaining
events are left queued for the next outer-loop iteration rather than
dropped. Quit/Ctrl-C now also breaks out of the drain immediately
after being handled, since there is no benefit to consuming further
buffered input before the outer loop can request managed shutdown.
Nils Andreas Svee