fix: Tool-Box mit sichtbarem Diff nicht mehr halbtransparent

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

wwwroot/css/chat.css

@@ -206,6 +206,10 @@
   opacity: var(--semi-transparent);
 }
 
+.tool-box:has(.tool-diff:not([hidden])) {
+  opacity: unset !important;
+}
+
 .tool-box-header {
   display: flex;
   align-items: center;