The expanded 里程碑详情 card was title+buttons only (60px) and showed no
diff context. Match TS image: grow it to 84px and add the diff status line
between title and buttons. The root commit shows '初始提交 — 没有父提交可对比'
(git.history.diff.initialCommit); later commits leave it blank until the
semantic node-diff summary lands.
- op-git: Commit.is_initial (parent_count == 0)
- op-editor-core: GitCommitSummary.is_initial
- op-host-desktop: plumb is_initial into the snapshot
- op-editor-ui: CARD_H 60→84, button row drops to +52, conditional diff line
fa2f200d9a