chore(i): some some general updates

apps/test/content/posts/katex-test.md

@@ -71,3 +71,11 @@ $$ \ce{CO2 + C -> 2 CO} $$
 $$ \ce{Hg^2+ ->[I-] HgI2 ->[I-] [Hg^{II}I4]^2-} $$
 
 $$C_p[\ce{H2O(l)}] = \pu{75.3 J // mol K}$$
+
+## $\KaTeX$ in headings
+
+This is a bug:
+
+```latex
+## $\KaTeX$ in headings
+```

apps/test/content/posts/mathjax-test.md

@@ -118,6 +118,12 @@ U \ar@/_/[ddr]_y \ar@{.>}[dr]|{\langle x,y \rangle} \ar@/^/[drr]^x \\
 \end{xy}
 $$
 
+## \$\\text{MathJax}\$ in headings
+
+```latex
+## \$\\text{MathJax}\$ in headings
+```
+
 ## More
 
 ### Dark Mode Adaptation

assets/css/_core/_widgets/_scrollbar.scss

@@ -1,7 +1,7 @@
 /* Modern browsers with `scrollbar-*` support (high priority) */
 @supports (scrollbar-width: auto) {
   * {
-    scrollbar-color: fixit-var(scrollbar-thumb-color) fixit-var(scrollbar-track-color);;
+    scrollbar-color: fixit-var(scrollbar-thumb-color) fixit-var(scrollbar-track-color);
     scrollbar-width: fixit-var(scrollbar-width);
   }
 }

assets/css/_page/_single/_code.scss

@@ -615,7 +615,7 @@ pre {
         font-weight: bold;
         color: fixit-var(secondary);
         white-space: nowrap;
-        user-select: none;
+        @include user-select(none);
         @include border-radius;
 
         // mobile style

assets/css/_page/_single/_diagram-copy-btn.scss

@@ -13,7 +13,6 @@
   right: 0.5rem;
   line-height: 1;
   padding: 0.5rem;
-  user-select: none;
   border: 1px solid;
   color: fixit-var(dcb-color, #25292e);
   border-color: fixit-var(dcb-border-color, #d1d9e0);
@@ -21,6 +20,7 @@
   box-shadow: fixit-var(dcb-box-shadow, 0px 1px 0px 0px #1f23280a);
   transition-duration: 0.1s;
   transition-property: color, background-color, box-shadow, border-color;
+  @include user-select(none);
   @include border-radius;
   @include z-index(base);
   @extend .print-d-none;