Drop redundant top-right nav from docs pages

The left sidebar already covers Install / Integrate / Wire format /
Operate across its four groups (Get started, Concepts, Reference,
Operate). The top-right nav duplicated those links one level up. On
mobile it was already hidden via @media rule, so the sidebar was
always the canonical navigation. Now it's the only navigation —
cleaner topbar, no duplication.

integrate.html

@@ -12,12 +12,6 @@
 <div class="topnav">
   <a href="https://keysat.xyz" class="brand" title="Back to keysat.xyz"><img src="assets/keysat-mark.svg" alt=""><span>Keysat</span></a>
   <span class="docs-tag">Docs</span>
-  <nav>
-    <a href="install.html">Install</a>
-    <a href="integrate.html" class="active">Integrate</a>
-    <a href="wire-format.html">Wire format</a>
-    <a href="operate.html">Operate</a>
-  </nav>
 </div>
 
 <div class="layout">