fix(blocks): Do not copy snippet when preview text is selected

#18611

This patch introduces skip conditional for the "copy code snippet
by shortcut key" feature.

this condition would not work when the preview is iframe (user sets
`docs: { inlineStories: false }`), but that does not matter as the
event handler won't run in the first place.

code/ui/blocks/src/components/Preview.tsx

@@ -223,6 +223,14 @@ export const Preview: FC<PreviewProps> = ({
   }, []);
 
   const onCopyCapture = (e: ClipboardEvent<HTMLInputElement>) => {
+    // When the selection range is neither empty nor collapsed, we can assume
+    // user's intention is to copy the selected text, instead of the story's
+    // code snippet.
+    const selection: Selection | null = globalWindow.getSelection();
+    if (selection && selection.type === 'Range') {
+      return;
+    }
+
     e.preventDefault();
     if (additionalActionItems.filter((item) => item.title === 'Copied').length === 0) {
       copyToClipboard(source.props.code).then(() => {