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/plugins/agentcli/plugin_test.go

@@ -31,7 +31,12 @@ func (tc *toolCapture) RegisterAPI(name string) error                          {
 func setupPlugin() (*Plugin, *toolCapture, error) {
 	p := New("agentcli")
 	tc := newToolCapture()
-	sdk := sdk.New("agentcli", sdk.SDKConfig{RegTool: tc.RegisterTool, RegStage: tc.RegisterStage, RegAPI: tc.RegisterAPI})
+	sdk := sdk.New("agentcli", sdk.SDKConfig{
+		RegTool:  tc.RegisterTool,
+		RegStage: tc.RegisterStage,
+		RegAPI:   tc.RegisterAPI,
+		Settings: sdk.NewSettings("agentcli", nil),
+	})
 	if err := p.Start(sdk); err != nil {
 		return nil, nil, err
 	}