fix(cli): respect stdin override in Scanln

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/cli/output.go

@@ -132,7 +132,7 @@ func Label(word, value string) {
 
 // Scanln reads from stdin.
 func Scanln(a ...any) (int, error) {
-	return fmt.Scanln(a...)
+	return fmt.Fscanln(newReader(), a...)
 }
 
 // Task prints a task header: "[label] message"

pkg/cli/output_test.go

@@ -141,3 +141,21 @@ func TestSection_GlyphTheme(t *testing.T) {
 		t.Fatalf("expected glyph theme to avoid unicode dashes, got %q", out)
 	}
 }
+
+func TestScanln_UsesOverrideStdin(t *testing.T) {
+	SetStdin(strings.NewReader("hello\n"))
+	defer SetStdin(nil)
+
+	var got string
+	n, err := Scanln(&got)
+
+	if err != nil {
+		t.Fatalf("Scanln returned error: %v", err)
+	}
+	if n != 1 {
+		t.Fatalf("expected 1 scanned item, got %d", n)
+	}
+	if got != "hello" {
+		t.Fatalf("expected %q, got %q", "hello", got)
+	}
+}