/// Main-actor reentrancy can interleave two async publication sequences even
/// though each individual operation is actor-isolated. Coalesce requests while
/// retaining one owner of source retirement, snapshot creation and publication.
@MainActor final class DocumentPublication {
    private var running = false
    private var requested = false
    func run(_ operation: @MainActor () async -> Void) async {
        requested = true
        guard !running else { return }
        running = true
        defer { running = false }
        while requested {
            requested = false
            await operation()
        }
    }
}