Enable sass parser in ui/build to parse indirect color assignments

The sass build for colors currently only works for direct assignments,
but doesn't work correctly when being assigned to another variables and
causes the assignee to be #000 instead.

ui/.build/src/sass.ts

@@ -235,16 +235,30 @@ async function parseScss(src: string) {
 async function parseThemeColorDefs() {
   const themeFiles = await globArray('./common/css/theme/_*.scss', { absolute: false });
   const themes: string[] = ['dark'];
+  const capturedColors = new Map<string, string>();
   for (const themeFile of themeFiles ?? []) {
     const theme = /_([^/]+)\.scss/.exec(themeFile)?.[1];
     if (!theme) {
       env.log(`${errorMark} - invalid theme filename '${c.cyan(themeFile)}'`, { ctx: 'sass' });
       continue;
     }
     const text = fs.readFileSync(themeFile, 'utf8');
-    const colorMap = new Map<string, clr.Instance>();
     for (const match of text.matchAll(/\s\$c-([-a-z0-9]+):\s*([^;]+);/g)) {
-      colorMap.set(match[1], clr(match[2]));
+      capturedColors.set(match[1], match[2]);
+    }
+    const colorMap = new Map<string, clr.Instance>();
+    for (const [color, colorVal] of capturedColors) {
+      let val = colorVal;
+      const visitedVariables = new Set();
+      while (val.startsWith('$')) {
+        const inferredValue = capturedColors.get(val.substring(3)) ?? '#000';
+        if (visitedVariables.has(inferredValue)) {
+          break;
+        }
+        visitedVariables.add(inferredValue);
+        val = inferredValue;
+      }
+      colorMap.set(color, clr(val));
     }
     if (theme !== 'default') themes.push(theme);
     themeColorMap.set(theme, colorMap);