fix(cli): reset stdin on nil override

pkg/cli/prompt.go

@@ -13,7 +13,14 @@ import (
 var stdin io.Reader = os.Stdin
 
 // SetStdin overrides the default stdin reader for testing.
-func SetStdin(r io.Reader) { stdin = r }
+// Pass nil to restore the real os.Stdin reader.
+func SetStdin(r io.Reader) {
+	if r == nil {
+		stdin = os.Stdin
+		return
+	}
+	stdin = r
+}
 
 // newReader wraps stdin in a bufio.Reader if it isn't one already.
 func newReader() *bufio.Reader {

pkg/cli/prompt_test.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"os"
 	"strings"
 	"testing"
 
@@ -50,3 +51,14 @@ func TestMultiSelect_Good(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, []string{"a", "c"}, vals)
 }
+
+func TestSetStdin_Good_ResetNil(t *testing.T) {
+	original := stdin
+	t.Cleanup(func() { stdin = original })
+
+	SetStdin(strings.NewReader("hello\n"))
+	assert.NotSame(t, os.Stdin, stdin)
+
+	SetStdin(nil)
+	assert.Same(t, os.Stdin, stdin)
+}