fix: restore icon color on FontChange trigger button

<button> defaults to color: ButtonText (black) in browsers, unlike <a>
which inherits. Adding color: inherit restores the theme color for the
SVG stroke (which uses currentColor).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/HeaderNote.vue

@@ -160,5 +160,9 @@ defineProps<{ user: string; repo: string }>()
   align-items: center;
   justify-content: space-between;
   margin-top: 10px;
+
+  button {
+    color: inherit;
+  }
 }
 </style>