Fix Sass fallback to pass implementation object

Ensure sass-loader receives the correct implementation in CJS/ESM environments by using mod.default || mod when falling back to 'sass'. This aligns with the 'sass-embedded' path and avoids interop pitfalls. No functional output changes are expected; this improves compatibility and reduces deprecation warnings in some environments

Author: PeterDaveHello

build.mjs

@@ -95,9 +95,8 @@ async function runWebpack(isWithoutKatex, isWithoutTiktoken, minimal, sourceBuil
     sassImpl = mod.default || mod
   } catch (e) {
     const mod = await import('sass')
-    // Prefer namespace import style to avoid deprecated default import warning
-    // "import sass from 'sass'" is deprecated; use namespace instead
-    sassImpl = mod
+    // Ensure we pass the implementation object regardless of ESM/CJS interop
+    sassImpl = mod.default || mod
   }
 
   const dirKey = path.basename(sourceBuildDir || outdir)