feat: Add comprehensive dark mode support for chart thumbnails and examples (#35111)

Co-authored-by: Claude <noreply@anthropic.com>

superset-frontend/plugins/legacy-plugin-chart-parallel-coordinates/src/index.js

@@ -19,8 +19,11 @@
 import { t, ChartMetadata, ChartPlugin } from '@superset-ui/core';
 import transformProps from './transformProps';
 import thumbnail from './images/thumbnail.png';
+import thumbnailDark from './images/thumbnail-dark.png';
 import example1 from './images/example1.jpg';
+import example1Dark from './images/example1-dark.jpg';
 import example2 from './images/example2.jpg';
+import example2Dark from './images/example2-dark.jpg';
 import controlPanel from './controlPanel';
 
 const metadata = new ChartMetadata({
@@ -29,10 +32,14 @@ const metadata = new ChartMetadata({
   description: t(
     'Plots the individual metrics for each row in the data vertically and links them together as a line. This chart is useful for comparing multiple metrics across all of the samples or rows in the data.',
   ),
-  exampleGallery: [{ url: example1 }, { url: example2 }],
+  exampleGallery: [
+    { url: example1, urlDark: example1Dark },
+    { url: example2, urlDark: example2Dark },
+  ],
   name: t('Parallel Coordinates'),
   tags: [t('Directional'), t('Legacy'), t('Relational')],
   thumbnail,
+  thumbnailDark,
   useLegacyApi: true,
 });