Prevent the navbar toggler icon middle bar from flex-shrinking

.changeset/navbar-toggler-squeeze.md

@@ -0,0 +1,5 @@
+---
+"@tabler/core": patch
+---
+
+Fixed the `navbar-toggler` icon: the middle bar was flex-squeezed, breaking the open-state X and shortening the hamburger.

core/scss/layout/_navbar.scss

@@ -446,6 +446,10 @@ Navbar toggler
 
 .navbar-toggler-icon {
   position: relative;
+  // The button's padding leaves less room than the bar is wide — without
+  // this the middle bar gets flex-squeezed while the pseudo bars keep their
+  // inherited width, and the open-state X loses a leg.
+  flex-shrink: 0;
   width: 1.25em;
   height: 2px;
   background: currentColor;