brand: the icon wears the theme

The cursor beside ~/ was a tall block in the alarm colour, the one hue the
theme keeps for something wrong, and the tilde was a hand-drawn wobble.
The mark is now drawn in the theme's light alone on its hull: a symmetric
tilde, the slash, and the underscore cursor the boot screen waits with,
inside the corner brackets the desktop frames things in. The touch icon,
the 512 px copy and the banner are rendered from the same SVG.

web/public/favicon.svg

@@ -1,14 +1,12 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
-  <!-- ~/ and a block cursor: the prompt the app is named after. -->
-  <defs>
-    <linearGradient id="hull" x1="0" y1="0" x2="0" y2="1">
-      <stop offset="0" stop-color="#181b17"/>
-      <stop offset="1" stop-color="#0c0d0b"/>
-    </linearGradient>
-  </defs>
-  <rect width="512" height="512" rx="112" fill="url(#hull)"/>
-  <rect x="22" y="22" width="468" height="468" rx="92" fill="none" stroke="#2a2f28" stroke-width="8"/>
-  <path d="M64 282 C86 226 128 220 158 254 C188 288 228 282 250 226" fill="none" stroke="#eef1ea" stroke-width="40" stroke-linecap="round"/>
-  <path d="M332 136 L274 376" fill="none" stroke="#eef1ea" stroke-width="40" stroke-linecap="round"/>
-  <rect x="360" y="150" width="88" height="212" rx="12" fill="#c8684f"/>
+  <!-- ~/ and the cursor the boot screen waits with, in the theme's one light
+       on its hull, inside the corner brackets the desktop frames things in. -->
+  <rect width="512" height="512" rx="112" fill="#0c0d0b"/>
+  <rect x="12" y="12" width="488" height="488" rx="100" fill="none" stroke="#2a2f28" stroke-width="6"/>
+  <path d="M60 116 V60 H116 M396 60 H452 V116 M452 396 V452 H396 M116 452 H60 V396" fill="none" stroke="#383e35" stroke-width="6"/>
+  <g fill="none" stroke="#eef1ea" stroke-width="30" stroke-linecap="square" stroke-linejoin="round">
+    <path d="M100 276 C100 244 118 230 138 230 C168 230 172 274 202 274 C222 274 240 260 240 228"/>
+    <path d="M318 160 L262 352"/>
+  </g>
+  <rect x="340" y="320" width="76" height="32" fill="#eef1ea"/>
 </svg>