fix(client): correct placement of Interactive Editor button (#64350)

Co-authored-by: Huyen Nguyen <25715018+huyenltnguyen@users.noreply.github.com>

client/src/templates/Challenges/classic/classic.css

@@ -83,6 +83,8 @@
 .tabs-row-right {
   display: flex;
   justify-content: flex-end;
+  /* Ensure the right group pins to the end even when no left/middle items exist */
+  margin-inline-start: auto;
 }
 
 .monaco-editor-tabs button + button {