Tighten nav-utilities spacing

- Reduce nav-utilities gap from 16px to 12px
- Reduce nav-tools gap from 12px to 6px

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/css/index.css

@@ -743,7 +743,7 @@ header h1 {
 .nav-utilities {
     display: none;
     align-items: center;
-    gap: 16px;
+    gap: 12px;
     margin-left: auto;
     flex-shrink: 0;
 }
@@ -785,7 +785,7 @@ header h1 {
 .nav-tools {
     display: flex;
     align-items: center;
-    gap: 12px;
+    gap: 6px;
     flex-shrink: 0;
 }