feat: add tray layout controls

internal/config/config_test.go

@@ -3,6 +3,7 @@ package config
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -64,6 +65,37 @@ func TestMissingActiveLayoutFails(t *testing.T) {
 	}
 }
 
+func TestLayoutNamesAreUniqueAndOrdered(t *testing.T) {
+	c := Default()
+	c.Layouts = append(c.Layouts,
+		Layout{Name: "Columns", Monitor: `\\.\DISPLAY2`},
+		Layout{Name: "Rows", Monitor: "*"},
+	)
+	got := c.LayoutNames()
+	if len(got) != 2 || got[0] != "columns" || got[1] != "Rows" {
+		t.Fatalf("unexpected names: %#v", got)
+	}
+}
+
+func TestSetActiveLayoutPreservesConfiguration(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "fancywin.yaml")
+	original := "# keep this comment\r\nversion: 1\r\nactive_layout: old # old value\r\nlayouts: []\r\n"
+	if err := os.WriteFile(path, []byte(original), 0o640); err != nil {
+		t.Fatal(err)
+	}
+	if err := SetActiveLayout(path, "new layout"); err != nil {
+		t.Fatal(err)
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	text := string(data)
+	if !strings.Contains(text, "# keep this comment\r\n") || !strings.Contains(text, "active_layout: new layout\r\n") || !strings.Contains(text, "layouts: []\r\n") {
+		t.Fatalf("unexpected rewritten file: %q", text)
+	}
+}
+
 func TestExcluded(t *testing.T) {
 	c := Default()
 	c.Excluded = []string{"notepad", "exact.exe"}