fusion/.changeset/fn-5644-merge-commit-summary-default-docs.md

@runfusion/fusion

@runfusion/fusion
patch

Update useAiMergeCommitSummary docs/JSDoc to match the intended default of true, including that merge commit summaries include a subject plus body summary (narrative + bullets + diff-stat).

Also fixes AI merge-mode prompt guidance so AI-authored squash commits include a summarized body instead of subject-only commit messages.