Add bot to play against.

web/src/styles.css

@@ -371,6 +371,17 @@ h3 {
   gap: 10px;
 }
 
+/* The three computer-opponent difficulty buttons share the row evenly. */
+.home-bots {
+  display: flex;
+  gap: 10px;
+}
+
+.home-bots .btn {
+  flex: 1;
+  white-space: nowrap;
+}
+
 .home-error {
   color: var(--red-soft);
   font-weight: 700;
@@ -479,6 +490,12 @@ h3 {
   background: var(--red);
 }
 
+/* Bots swap the connection dot for a little robot face. */
+.bot-dot {
+  font-size: 0.85rem;
+  line-height: 1;
+}
+
 /* The room code, stamped like a label on a card tray. */
 .topbar-code {
   font-family: var(--font-display);