feat: restructure plugin system, add Lua plugin support, update docs

internal/plugin/dynamic_dll_test.go

@@ -0,0 +1,32 @@
+//go:build windows
+
+package plugin
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestTryLoadDLL_NoFile(t *testing.T) {
+	dir := t.TempDir()
+	plg, err := tryLoadDLL(dir, "nonexistent", nil)
+	if err != nil {
+		t.Fatalf("tryLoadDLL on empty dir should not error: %v", err)
+	}
+	if plg != nil {
+		t.Fatal("expected nil for non-existent plugin.dll")
+	}
+}
+
+func TestTryLoadDLL_Invalid(t *testing.T) {
+	dir := t.TempDir()
+	os.WriteFile(filepath.Join(dir, "plugin.dll"), []byte("not a real dll"), 0644)
+
+	plg, err := tryLoadDLL(dir, "baddll", nil)
+	t.Logf("plg=%v err=%v", plg, err)
+
+	if err == nil && plg == nil {
+		t.Fatal("expected error or non-nil plugin for existing file")
+	}
+}