Development record

The worktree store's merged judgement keeps for good a branch whose merge it cannot see from the reflog or the forge: a branch rebased locally and then merged leaves no commit entry of its own in its reflog, and so does a merged branch whose reflog has expired; with no forge answer the content tests are always false once the tip is an ancestor of the default branch, so prune keeps the worktree on every run although its work has landed. Found by the Opus review of the store's steps 3 and 4 on 2026-10-23; it errs on the safe side, never reclaiming what it cannot prove.