Simplify GUI settings and build flags

internal/config/config_test.go

@@ -3,6 +3,7 @@ package config
 import (
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -31,3 +32,44 @@ func TestLoadOSCValues(t *testing.T) {
 	}
 }
 
+func TestLoadGUIValues(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.toml")
+	if err := os.WriteFile(path, []byte("[gui]\ntop_most = true\nfont_size = 24\n"), 0o600); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+	cfg, err := Load(path)
+	if err != nil {
+		t.Fatalf("Load returned error: %v", err)
+	}
+	if cfg.GUI.TopMost != true || cfg.GUI.FontSize != 24 {
+		t.Fatalf("unexpected gui values: %+v", cfg.GUI)
+	}
+}
+
+func TestSaveGUIUpdatesSection(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.toml")
+	initial := []byte("[self]\nname = \"alice\"\n\n[gui]\ntop_most = false\nfont_size = 18\n")
+	if err := os.WriteFile(path, initial, 0o600); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+	if err := SaveGUI(path, GUIConfig{TopMost: true, FontSize: 26}); err != nil {
+		t.Fatalf("SaveGUI returned error: %v", err)
+	}
+	cfg, err := Load(path)
+	if err != nil {
+		t.Fatalf("Load returned error: %v", err)
+	}
+	if cfg.GUI.TopMost != true || cfg.GUI.FontSize != 26 {
+		t.Fatalf("unexpected saved gui values: %+v", cfg.GUI)
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	text := string(data)
+	if !strings.Contains(text, "[self]") || !strings.Contains(text, "name = \"alice\"") {
+		t.Fatalf("non-gui config content was lost: %s", text)
+	}
+}