Clicking "Copy SQL to Clipboard" should give stronger indication of errors

When clicking the "Copy SQL to Clipboard" icon in the heading, the VSCode extension also shows a "Copied SQL to Clipboard" message.

But it shows that message even if there are errors in the PRQL query. A better behavior would be to give a different error indication ("THIS DIDN'T WORK!") so that I don't get fooled into thinking the contents of the clipboard are what I want.

