Add WaitingForChildren to the CancelAsync guard so a parent waiting on its
children can be cancelled.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
A finalized planning parent now joins the unified parent lifecycle:
WaitingForChildren while its child chain runs (or WaitingForReview directly
if it has no children), advancing to review like an improvement parent.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Collapse TryCompleteParentAsync (planning -> Done) and
TryAdvanceImprovementParentAsync (improvement -> WaitingForReview) into one
TryAdvanceParentAsync that surfaces any WaitingForChildren parent for review
once all children are terminal. Planning parents no longer auto-complete.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
