ui: Move styles/ to $lib scope (#26950)

* refactor: Move `styles/` to `src/lib` and remove legacy alias

* chore: Add newline

tools/ui/src/lib/styles/katex-custom.scss

@@ -0,0 +1,16 @@
+// Override KaTeX SCSS variables to disable ttf and woff fonts
+// Only use woff2 format which is embedded in the bundle
+$use-woff2: true;
+$use-woff: false;
+$use-ttf: false;
+
+// Use Vite alias for font folder
+$font-folder: 'katex-fonts';
+
+// Import KaTeX SCSS with overridden variables
+@use 'katex/src/styles/katex.scss' with (
+	$use-woff2: true,
+	$use-woff: false,
+	$use-ttf: false,
+	$font-folder: 'katex-fonts'
+);