- PREPARATION_COMMAND_TIMEOUT_MS (900 s) applies only to acquisition and
offline dependency commands; everything else keeps COMMAND_TIMEOUT_MS
(300 s), and both are cut to the journey deadline
- prepared-tree export refusals fail with PREPARED_EXPORT_REJECTED and the
helper's fixed reason or errno, never target paths, with no retry
- free tests pin the ceiling, its callers, and the rejection parser