Unpin Evaluation From Constitution

Remove a belief from the Constitution (TOS-1412).

Unpinning never touches confirmed or protection_level - the belief stays held-true and keeps competing through the attention package; it just stops being always-on. Locked (constitutional-seed) rows are Constitution members via protection_level='locked', not via the pin, so unpinning cannot remove them - by design (they are the non-negotiable core).

TOS-1982 Phase 2: a real True->False transition also emits an ELEVATE constitution_unpin event, regardless of whether the pin being removed was applied by a human or by the constitution-candidacy auto-pin sweep. This is a durable veto - see constitution_candidacy. was_constitution_unpinned - so a LATER consolidation pass never silently re-pins this SAME evaluation even if it still satisfies every auto-pin criterion. The user retains the ordinary manual pin route to re-add it at any time; only the AUTOMATIC sweep is vetoed.