Release v19.59.2

Changed

• The concurrency documentation explains how a generated identifier is guaranteed to be new with a scope that expects no prior events, how batches and storage retries check that scope, what happens on a collision, and when to use a unique constraint or a deterministic identifier instead (#4713)

Fixed

• Appending a batch with two concurrency scopes for the same event source no longer fails with a generic error: identical scopes are merged and conflicting ones are rejected with a clear append error (#4712)