Supersede Autopost Decision

Let the AI code a reversed document again (accountant).

The explicit user action the coder deliberately will not take on its own: its claim predicate has no reversal escape hatch, so a wrong AI booking that a human reversed is otherwise never re-proposed (doc/pipeline.md §"Invoice coding (phase 2)"). Clears the superseded autopost:code: decision; the coder picks the item up on its next sweep and proposes from scratch. The decision row itself is destroyed — that IS the mechanism — while the journal keeps the full reversal audit trail.

409 when the booking still stands (including a reversal that was itself reversed), when the row is a human manual:code: booking or booked nothing, when the document still carries a live recognition plan, or when something else on the item (a capitalization, an accrual, a linked expense receipt…) would keep the coder from re-claiming it anyway. 404 for an unknown decision or a deleted item.