Strict FIFO task pipeline and propagating trust revocation

Task pipeline now executes strictly FIFO. Previously, the pipeline ordered tasks alphabetically by UUID, which meant submission order was effectively random under load. `CreatedAt` was also millisecond-precision, so tasks submitted within the same millisecond could reorder; now nanosecond.

The submitter auto-cancels on accept timeout — previously left dangling. Trust revocation now propagates to the remote peer rather than staying local. `pilotctl task result` surfaces delivered payloads, and `status_justification` is exposed in `task list`.