PlanningMergeOrchestrator._states is in-memory. A worker restart during a
conflict pause left the list repo mid-merge with no recovery path: both
ContinuePlanningMerge and AbortPlanningMerge threw "no in-progress merge",
and re-Approving failed on the IsMidMergeAsync guard.
AbortAsync now falls through to a stateless path when no _states entry exists:
it looks up the parent's list WorkingDir and, if the repo is mid-merge, runs
git merge --abort there directly, then broadcasts PlanningMergeAborted.
Parent remains WaitingForReview — the next Approve restarts the unit merge
(already-Merged child worktrees are skipped as before).
ContinueAsync error message now points to AbortPlanningMerge as the recovery
action. StartAsync mid-merge guard also carries an actionable hint.
Tests: AbortAsync stateless + mid-merge (restart recovery), AbortAsync
stateless + clean repo (clear error).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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