refactor: migrate built-in plugins to SDK-only interface

- Six-phase plan complete: webui/cli/healthcheck/pluginmgr/clawhubadapter
  now interact with the kernel exclusively via internal/sdk interfaces;
  all Configure() calls and package-level global injection removed
- buildSDK in internal/plugin/registry.go is the single assembly point
- Add internal/sdk/events.go exporting event types/constants
- Fix ProviderManager cooldown sharing: LuaAdaptedProvider.Name() now
  returns the source name instead of lua_<adapter>, so multiple sources
  sharing an adapter (single script load via shared VM AdapterCache) no
  longer share failure-cooldown state
- Verified: build/vet/tests green, deployed to homeagent.service with
  full plugin capability testing via local OpenAI-compatible mock

internal/sdk/adapter_impl.go

@@ -0,0 +1,62 @@
+package sdk
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+
+	luaVM "gitcode.com/JianFeeeee/HomeAgent/internal/lua"
+)
+
+// adapterImpl 桥接 Lua VM 的协议适配器管理。
+type adapterImpl struct {
+	vm *luaVM.VM
+}
+
+func NewAdapter(vm *luaVM.VM) AdapterAPI {
+	return &adapterImpl{vm: vm}
+}
+
+func (a *adapterImpl) List() []APIAdapter {
+	if a.vm == nil {
+		return nil
+	}
+	got := a.vm.ListAdapters()
+	out := make([]APIAdapter, len(got))
+	for i, ad := range got {
+		out[i] = APIAdapter{Name: ad.Name, Version: ad.Version}
+	}
+	return out
+}
+
+func (a *adapterImpl) Load(name, code string) error {
+	if a.vm == nil {
+		return errors.New("lua vm not available")
+	}
+	path := filepath.Join(a.vm.AdapterDir(), name+".lua")
+	if err := os.WriteFile(path, []byte(code), 0644); err != nil {
+		return err
+	}
+	return a.vm.LoadAdapter(path)
+}
+
+func (a *adapterImpl) Remove(name string) error {
+	if a.vm == nil {
+		return errors.New("lua vm not available")
+	}
+	path := filepath.Join(a.vm.AdapterDir(), name+".lua")
+	if err := os.Remove(path); err != nil {
+		return err
+	}
+	a.vm.RemoveAdapter(name)
+	return nil
+}
+
+func (a *adapterImpl) AdapterDir() string {
+	if a.vm == nil {
+		return ""
+	}
+	return a.vm.AdapterDir()
+}
+
+var _ AdapterAPI = (*adapterImpl)(nil)