Fixed ~24px caret-line cells bookend the status bar (left=sidebar, right=context);
chevron flips per arrangement.isCollapsed (inward=collapse, outward=expand) and
fires the existing sidebar.collapse / context.collapse commands — the mouse
affordance for the already keyboard/CLI-addressable action (D-6). Visual only;
no new collapse logic. Status items shift 28px inward for the reserved cells.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8