v4.15.2

Nuthatch 4.15.2 changes one default: a nest started without --poll-interval now asks for the tip every
5 minutes instead of at the chain's block time. It is 4.15.1 plus that change.

A nest polls every 5 minutes unless told otherwise

Every poll is billed whether or not a block carried an event: a tip call, and when a window commits, a
reorg check, a checkpoint and a finalized probe. An idle nest on a metered endpoint spent most of its
cost polling. Until now an unset --poll-interval meant the chain's block time, never under 2 s, so a
nest polled every 2 to 12 seconds. The openloom-bsc stopgap nest, polling once a minute, costs about
$3 a month on Alchemy at rest; at 5 minutes the polling cost falls to a fifth of that.

Without the flag a caught-up cursor now waits 5 minutes, or the block time if that is longer, which no
registry chain's is. New rows can take up to 5 minutes to appear. A nest whose readers need the
tip closely passes a shorter interval, for example --poll-interval 2s, exactly as before (#1995).

/ready is unchanged: freshness.poll_interval_secs reports 300 for a defaulted interval, and
poll_interval_source stays block_time for a default and flag for an explicit one.

Gated on Lodestar's data

Every production Lodestar nest already passes --poll-interval 5m, so none of them changes behaviour.

Compatibility and upgrade

Replace the binary and restart. No re-index and no configuration change. To keep the old cadence on a
nest that relied on it, add --poll-interval with the chain's block time.