fix(ui): add Cmd+Enter save shortcut to issue description editor

Pass onSubmit={commit} to MarkdownEditor in InlineEditor's multiline
mode so Cmd/Ctrl+Enter triggers save when editing an issue description.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/InlineEditor.tsx

@@ -81,6 +81,7 @@ export function InlineEditor({
             placeholder={placeholder}
             contentClassName={className}
             imageUploadHandler={imageUploadHandler}
+            onSubmit={commit}
           />
           <div className="flex items-center justify-end gap-2">
             <Button