Adds border radius to AI explain box

Author: eamodio

src/webviews/apps/shared/styles/details-base.scss

@@ -381,6 +381,7 @@ ul {
 	background: var(--vscode-input-background);
 	margin-top: 1rem;
 	padding: 0.5rem;
+	border-radius: 2px;
 
 	&.has-error {
 		border-left-color: var(--color-alert-errorBorder);