Give a mark and a cursor five seconds rather than ten

Long enough to notice, short enough not to sit on the prose. Applies to
all three durations somebody actually sees: a mark once it has been read,
the agent's cursor after its turn ends, and the label naming it.

The renewal cadence stays where it is. It is a heartbeat sized against
the thirty seconds after which a peer drops a state, not a length of time
anything is shown for, and halving it would only double the traffic.