Sidebar was a small strip in the middle of the page. Now it lives on
the left edge as a proper column, sized to be reachable — 220px full
mode with icon + label per link, on the operator's brand backdrop.
Breakpoints:
>1180px full sidebar, icon + label, "ON THIS PAGE" section header
<=1180px 64px icon rail, labels drop, tooltips on hover
<=720px bottom bar strip, icons only, spans page width
body padding-left carries the sidebar width so the topnav and page
content flow as one column beside the rail — no overlap on any width.
Home has 4 icons (What it is / Features / Download / Verify), Plug-ins
has 3 (Aegis / Ariadne's Thread / vs extensions), Extensions has 6
(Bundled / Community / Build & publish / Updates / Operator key /
Roadmap).
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