Round 2 of the deep review, on round 1's own fixes:
- `ORDER BY position … FOR UPDATE` sorts before it locks, so the reorder that waited got the
fresh rows in its STALE order and dealt the pins it left out (a tab with Plex off) back to their
old slots. It locks in id order — one global order, so two reorders cannot deadlock — and sorts
the fresh rows itself. The race test now sends that partial list and fails unless tab B really
blocked.
- The request check saw only writes the handler flushed: a `db.delete` left staged, or a flush
followed by a released savepoint, passed. Staged changes count at the end of the request, and
only the ROOT transaction's end clears it (a savepoint test drives the dependency directly).
- The `ok` test exempted every call as a serializer, hiding four domain REPORTS (YouTube sync,
revert, push; Plex sync) without `ok`. They are spread into `{"ok": True, …}`; the exemption is a
named list of real serializers.
peter
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