Replace panel tileKey with a direct color prop.

Drop theme panelTiles keys and the ArticleView update callback wiring.

src/components/article/ArticlePhotoTile.jsx

@@ -78,7 +78,7 @@ class ArticlePhotoTile extends Component {
       wide = 1,
       minHeight = 200,
       sx,
-      tileKey,
+      color,
     } = this.props;
     const { busy, editOpen } = this.state;
     const photo = primaryPhoto(articleData);
@@ -90,7 +90,7 @@ class ArticlePhotoTile extends Component {
           wide={wide}
           minHeight={minHeight}
           sx={sx}
-          tileKey={tileKey}
+          color={color}
           action={
             hasPhoto
               ? {