feat: support named switchable layouts

internal/config/config_test.go

@@ -1,6 +1,10 @@
 package config
 
-import "testing"
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
 
 func TestDefaultValid(t *testing.T) {
 	if err := Default().Validate(); err != nil {
@@ -15,6 +19,51 @@ func TestLayoutFallback(t *testing.T) {
 	}
 }
 
+func TestActiveLayoutSelection(t *testing.T) {
+	c := Default()
+	c.Layouts = append(c.Layouts, Layout{Name: "wide", Monitor: "*", Zones: []Zone{{Name: "wide", Width: 100, Height: 100}}})
+	c.ActiveLayout = "wide"
+	got, ok := c.LayoutFor(`\\.\DISPLAY1`)
+	if !ok || got.Name != "wide" || len(got.Zones) != 1 {
+		t.Fatalf("wrong active layout: %+v, %v", got, ok)
+	}
+}
+
+func TestLegacyLayoutUpgrade(t *testing.T) {
+	c := Default()
+	c.ActiveLayout = ""
+	for i := range c.Layouts {
+		c.Layouts[i].Name = ""
+	}
+	c.upgradeLegacyLayouts()
+	if c.ActiveLayout != "default" || c.Layouts[0].Name != "default" {
+		t.Fatalf("legacy layout was not upgraded: %+v", c)
+	}
+}
+
+func TestLoadLegacyUnnamedLayout(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "legacy.yaml")
+	data := []byte("version: 1\ngap: 8\nshift_drag: true\nlayouts:\n  - monitor: '*'\n    zones:\n      - {x: 0, y: 0, width: 100, height: 100}\n")
+	if err := os.WriteFile(path, data, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	c, err := Load(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.ActiveLayout != "default" || c.Layouts[0].Name != "default" {
+		t.Fatalf("legacy file was not upgraded: %+v", c)
+	}
+}
+
+func TestMissingActiveLayoutFails(t *testing.T) {
+	c := Default()
+	c.ActiveLayout = "missing"
+	if err := c.Validate(); err == nil {
+		t.Fatal("expected missing active layout to fail")
+	}
+}
+
 func TestExcluded(t *testing.T) {
 	c := Default()
 	c.Excluded = []string{"notepad", "exact.exe"}