An AI-merge land of a branch with zero commits ahead of the integration
tip (the shape a coding agent that produced no commits leaves behind)
builds a clean-room worktree and runs a dependency install before
reaching the empty outcome via mergeAndReview. On a non-workspace land
the dep install throws hard, so the merge is transient-retried to
exhaustion (3/3) and the card is terminally parked failed.
Short-circuit on a CONFIDENT zero-ahead count (a git failure yields NaN
and falls through) and return the identical outcome:"empty" shape
before the throw-prone churn.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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