`idempotent()` was fixed to wrap anything `work()` throws, with a documented
rationale: this port's contract is `StudioGatewayError` only, so nothing else
may cross it. Its `read()` sibling was left unwrapped, so an uncharacterized
internal failure on any of the seven read operations escaped as a raw `Error`
and reached UI code written to catch `StudioGatewayError`.
`read()` now applies the same `failureOf` classification. It has no
idempotency ledger, so only the problem half is used. `boundary()` stays
outside the wrap so an aborted request still surfaces as `AbortError`,
exactly as `idempotent()` arranges it -- asserted by the new test.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
