A chain fork was detected, but the ClickHouse target has no onRollback handler, so the rows
written above the fork point cannot be removed. Returning a rewound cursor without removing them
would leave diverged data, so the target refuses instead. On the hot stream a startup warning
announces this risk before a fork ever arrives.
Fix — configure onRollback on the ClickHouse target. The typical implementation calls
store.removeAllRows with where: 'block_number > {latest:UInt32}' and
params: { latest: safeCursor.number }. A pipe reading /finalized-stream never forks and does
not need one.
