Root cause: AR retries book_outline when score < 60; each retry's package step
creates a new batch of chapters. InProgress chapters can't be deleted on rejection
so multiple sets accumulate. The boardroom deliberation (4 rounds) is the quality
gate — no retry needed at the outline level.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>