Decode Unicode variable names in CSS vars export block

The SCSS analyzer encodes non-ASCII characters as _u<hex>_ for parsing,
but cssVarsBlock emitted these encoded names into the CSS vars block.
Dart Sass then failed because the encoded names don't match the original
SCSS variable names. Decode before emitting so names round-trip correctly.

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

Author: cderv

src/core/sass/add-css-vars.ts

@@ -16,6 +16,14 @@ import { getVariableDependencies } from "./analyzer/get-dependencies.ts";
 
 const { getSassAst } = makeParserModule(parse);
 
+// Reverse the _u<hex>_ encoding applied in parse.ts so that
+// variable names emitted into the CSS vars block match the
+// original SCSS source that Dart Sass compiles against.
+const decodeScssName = (name: string) =>
+  name.replace(/_u([0-9a-f]+)_/g, (_, hex: string) =>
+    String.fromCodePoint(parseInt(hex, 16))
+  );
+
 export class SCSSParsingError extends Error {
   constructor(message: string) {
     super(`SCSS Parsing Error: ${message}`);
@@ -38,7 +46,8 @@ export const cssVarsBlock = (scssSource: string) => {
   for (const [dep, _] of deps) {
     const decl = ast.get(dep);
     if (decl.valueType === "color") {
-      output.push(`--quarto-scss-export-${dep}: #{$${dep}};`);
+      const originalName = decodeScssName(dep);
+      output.push(`--quarto-scss-export-${originalName}: #{$${originalName}};`);
     }
   }
   output.push("}");

tests/docs/smoke-all/2026/02/20/custom-14065-var.scss

@@ -0,0 +1,7 @@
+/*-- scss:defaults --*/
+$présentation-bg: #ff0000;
+
+/*-- scss:rules --*/
+#test-unicode-var {
+  background-color: $présentation-bg;
+}

tests/docs/smoke-all/2026/02/20/issue-14065-var.qmd

@@ -0,0 +1,15 @@
+---
+title: "Unicode SCSS Variable Test"
+format:
+  html:
+    theme:
+      - default
+      - custom-14065-var.scss
+_quarto:
+  tests:
+    html:
+      ensureCssRegexMatches:
+        - ['#test-unicode-var', 'background-color']
+---
+
+Content with a unicode-named color variable in SCSS.