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/memory_impl.go

@@ -50,6 +50,11 @@ func (m *graphMemory) Purge(criteria map[string]string, mode string) (int, error
 	return m.db.Purge(criteria, mode)
 }
 
+func (m *graphMemory) GraphData() (map[string]interface{}, error) {
+	if m.db == nil { return map[string]interface{}{}, nil }
+	return m.db.GraphData()
+}
+
 type textMemoryImpl struct{ tm *text.Memory }
 
 func NewTextMemory(tm *text.Memory) TextMemoryAPI { return &textMemoryImpl{tm: tm} }
@@ -61,6 +66,22 @@ func (m *textMemoryImpl) Append(evt TextEvent) error {
 	})
 }
 
+func (m *textMemoryImpl) RecentEvents(n int) ([]TextEvent, error) {
+	if m.tm == nil { return nil, nil }
+	got, err := m.tm.RecentEvents(n)
+	if err != nil { return nil, err }
+	out := make([]TextEvent, len(got))
+	for i, e := range got {
+		out[i] = TextEvent{Role: e.Source, Content: e.Input, Timestamp: e.Timestamp, Channel: e.AgentID}
+	}
+	return out, nil
+}
+
+func (m *textMemoryImpl) Stats() map[string]interface{} {
+	if m.tm == nil { return map[string]interface{}{} }
+	return m.tm.Stats()
+}
+
 type docMemoryImpl struct{ ds *doc.Store }
 
 func NewDocMemory(ds *doc.Store) DocMemoryAPI { return &docMemoryImpl{ds: ds} }