Significant state about forks is stored in ephemeral blockHistory

Rollbacks can only be initiated when the action reader sees them happening, with its occurrence stored in AbstractActionReader#blockHistory. If the indexState is on a forked block at startup, then the action reader will not have any way of knowing this and send a block whose blockHash does not match, and it is not trivial to determine how far the Handler needs to roll back.

Start by tracing AbstractActionReader#blockHistory and the startup handling of indexState, then inspect how Handler determines rollback depth when the indexed block is on a fork. Reproduce the forked-startup scenario and define the expected block-hash and rollback behavior before changing the state model; done means the Handler can recover deterministically without relying on ephemeral block history.