Top_nav_bar / bottom_nav / nav_chip_row covered mobile and inline
chrome but desktop dashboards still had to hand-roll their left
sidebar via batch_design. Adds a 240px-wide vertical rail with
icon+label rows, optional brand title, and slate-100 pill bg on the
active item — distinct surface from the existing nav tools so the
decision tree picks it cleanly for "sidebar / side nav / 侧边栏".
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