docs: clarify website product highlights

Reframe the feature section around the broader desktop product rather than only Agent Runtimes. Clarify official x64 and arm64 coverage, the separate LoongArch preview, and that compatibility claims are not vendor certification.

sites/en.html

@@ -72,7 +72,7 @@
 
         <nav class="site-navigation" id="site-navigation" aria-label="Main navigation" data-navigation>
           <a href="#download">Download</a>
-          <a href="#features">Agent Runtime</a>
+          <a href="#features">Highlights</a>
           <a href="#assistant">Desktop assistant</a>
         </nav>
 
@@ -289,7 +289,7 @@
         <div class="section-inner">
           <div class="section-heading">
             <div>
-              <p class="kicker">Agent Runtime</p>
+              <p class="kicker">Product highlights</p>
               <h2 id="features-title">Agent Runtimes in one desktop interface</h2>
             </div>
             <p>
@@ -321,8 +321,8 @@
                 </svg>
               </div>
               <span class="feature-number">02</span>
-              <h3>Built for desktop platforms</h3>
-              <p>Windows, macOS, and Linux releases are available for both x64 and arm64.</p>
+              <h3>Broad desktop architecture coverage</h3>
+              <p>Official Windows, macOS, and Linux releases cover x64 and arm64, with a separate experimental LoongArch preview.</p>
             </article>
 
             <article class="feature-card">