Production code (lib/): all Process.sleep calls replaced with receive
after timeout - retry backoff, exponential backoff, batch delays,
poll intervals, and settle waits.
Test code: poll_until helpers across 4 agent channel test files now
use receive after instead of Process.sleep. Various standalone
Process.sleep(N) calls replaced with :sys.get_state sync barriers
or receive after. deferred_discovery test simulation sleeps reduced
500ms -> 30ms.
