fix(website): keep the nav inside a 390px viewport

The brand, language switch, theme toggle and Get Maka button overflowed a 390px viewport by 4px, and the 中文 label wrapped onto two lines. Hero and downloads page carry the same call to action, so the button is dropped from the nav at phone widths, and the switch no longer wraps.

Generated-by: Claude Code

Author: Astro-Han

website/src/styles/site.css

@@ -97,6 +97,9 @@ code {
   align-items: center;
   gap: 4px;
 }
+.nav > * {
+  flex-shrink: 0;
+}
 .nav .brand {
   display: flex;
   align-items: center;
@@ -144,6 +147,7 @@ code {
   overflow: hidden;
   font-size: 12px;
   font-weight: 500;
+  white-space: nowrap;
 }
 .lang a,
 .lang span {
@@ -1003,6 +1007,13 @@ h2 {
   .wrap {
     padding: 0 20px;
   }
+  .nav .btn {
+    display: none;
+  }
+  .nav .brand,
+  .nav .theme {
+    margin-right: 0;
+  }
   .hero {
     padding-top: 40px;
   }