Merge the comments side-panel header into the Open/Resolved tab row to
save vertical space: title on the left, tabs centered, close button on
the right.
- comment-list-with-tabs: add optional `title`/`onClose` props; render
the title and close button as absolutely-positioned overlays around a
full-width centered Tabs.List. Keeping them outside Tabs.List preserves
the tablist ARIA contract (only role="tab" children) while the tab
list's full-width bottom border line is retained.
- aside: pass `title`/`onClose` to CommentListWithTabs for the comments
tab and drop the shared header for that tab; the toc/details tabs keep
their existing shared header and scroll area unchanged.
c83343d3a3