UI: restyle filter bar active state

app/styles/ui.scss

@@ -654,17 +654,10 @@
         position: absolute;
         bottom: 0;
         left: 50%;
-        width: 0;
-        height: 0;
+        width: 100%;
+        height: 3px;
         transform: translateX(-50%);
-        border-style: solid;
-        border-width: 0 10px 10px;
-        border-color: transparent transparent var(--brand-color--faint);
-      }
-
-      &::after {
-        bottom: -1px;
-        border-color: transparent transparent var(--foreground-color);
+        background-color: var(--accent-color);
       }
     }
   }