fix: reserve scrollbar gutter to avoid layout shift between tabs

web/src/app.css

@@ -3,6 +3,12 @@
   themes: dark --default;
 }
 
+/* Reserve space for the vertical scrollbar even when the page doesn't scroll,
+   so switching to a taller tab (e.g. Services) doesn't shift the layout. */
+html {
+  scrollbar-gutter: stable;
+}
+
 /* Markdown reader: tables scroll sideways instead of overflowing the card. */
 .prose table {
   display: block;