Changelog

0.4.0

Adds Slap.Cluster.status/2 to report the startup probe, shard lifecycle state, and retained failures, and Slap.Cluster.await_ready/2 to wait for every shard to finish starting. Cluster modules expose status/1 and await_ready/1.
Readiness checks remote owners and direct shard children, including child restarts. It reports lifecycle state without accessing storage; it does not check current storage reachability or write durability.
Timeouts cover the whole query or wait. Waits rediscover owners after placement changes, including when the timeout is :infinity.

Distributed routing ignores placements from a killed strategy while the cluster retries its background store probe or awaits a new placement round.
probe: :background starts the cluster before the store passes its probe. It retries after 1 s, backs off to at most 30 s, and opens shards only after a successful probe.
:settings maps from a cluster module's :defaults, the application environment, and start_link/1 are merged by key. Later sources override only the settings they contain.
A strategy start failure is now reported under the Slap.Cluster.Probe child id instead of :strategy; the reason is unchanged.

Uses slap_slatedb 0.2.0, which upgrades SlateDB from 0.16 to 0.17. Databases written by 0.1.0 open unchanged.

Initial release of slap_cluster.