Record that 2d's worked examples no longer exist

The registry reset deleted Lim Seonho and character_afa7623b, so there is nothing
to merge or split until the rerun mints a new set. What was done instead is the
safety net for that rerun, since reconcile runs inside it: a merge retires the
losing row rather than deleting it, and records which assignments moved.

Half-closes caveats/audit-open.md#destructive-reconcile. The unmerge path and the
split stay unwritten on purpose, with the revisit trigger named.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

caveats/audit-open.md

@@ -5,12 +5,22 @@ fixed findings live in `decisions/audit-phase1.md`. Line numbers are from the au
 
 ## Reconcile deletes the losing character irreversibly {#destructive-reconcile}
 
-Reconciliation deletes the losing character row (`db.py:506`). Clearing the reconcile stage does not
-undo it, and name claims attached to the merged-away character are not repointed.
+Reconciliation used to delete the losing character row. Clearing the reconcile stage did not undo it, and
+nothing recorded which detections had been the loser's.
 
-Costs: one bad merge is unrecoverable without rebuilding the identity stage for the whole manga.
-Revisit when: identity work resumes, or a reviewer reports a wrong merge on a real chapter.
-Workaround: none. Clear identity and rerun, which loses the good merges too.
+**Half-closed 2026-08-12.** The loss is no longer unrecoverable. `merge_characters` marks the loser
+`merged_into = keeper` instead of deleting it, so its embedding, description and gender survive, and every
+repointed assignment is stamped `method = merged_from:<loser_id>` in `identity_assignment_sources`. Those
+two records are enough to walk a merge backwards. Roster readers filter `merged_into IS NULL`. Lookup by
+id does not, so an assignment still pointing at a merged id resolves.
+
+What is still missing is the mechanism that consumes them: there is no unmerge, and no split. Undoing a
+merge today means a manual SQL walk of the two records above.
+
+Costs: a wrong merge needs hand-written SQL to undo, not a rebaseline.
+Revisit when: a reviewer reports a wrong merge, or the review gates from [#136] get a place to hang
+name/merge/split actions. No wrong merge has been seen since the crops were fixed, so building the unmerge
+before either trigger would be speculative.
 
 ## Clearing a stage does not undo what it wrote {#dishonest-clearing}