fix: return non-exit code when uc commands cancelled by not confirming prompt (fixes #354)

internal/cli/errors.go

@@ -0,0 +1,15 @@
+package cli
+
+// CancelledError signals an interactive command was aborted by the user at a confirmation prompt.
+type CancelledError struct {
+	Message string
+}
+
+func (e *CancelledError) Error() string {
+	return e.Message
+}
+
+// Cancelled returns a CancelledError carrying the given user-facing message.
+func Cancelled(msg string) error {
+	return &CancelledError{Message: msg}
+}