[bgentry]

An extension that coordinates peer jobs works each peer itself, so the client's work hooks never run for peers. That includes hooks that decode job arguments. Insertion extensions also need resolved options in insert hooks, and they need to see unique duplicates after an insertion returns an existing row.

This adds PeerAttempts::work_begin and work_end to the unstable extension module. They run the client's hooks in registration order and stop at the first failing begin hook, as the executor does. Errors keep their original type through hooks and outcomes, so hooks and the error handler can downcast them. A JobCancelError in a peer's error cancels the peer, as it does for a job whose worker returns it. The executor's own begin-hook errors also skip the extra wrapper now.

The internal option trait now exposes resolved insertion options. After persistence, after_jobs_inserted gets every returned row in input order, including unique duplicates. Each row comes with its requested metadata and a flag that marks an existing duplicate. An extension can then base its bookkeeping on the stored row or on the request, within the same transaction.

ProducerClaimNext::claim_at_most lets a producer session claim fewer jobs than River's limit. The limit caps the requested maximum, a zero maximum runs no query, and the continuation is consumed either way.

JavaScript already applies argument read transforms when it claims peers, so it needs no peer-hook change.