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/tracker.go

@@ -0,0 +1,36 @@
+package sdk
+
+import "time"
+
+// TrackerAPI provides access to the file change tracker / rollback.
+type TrackerAPI interface {
+	ChangeSets() []*ChangeSet
+	Rollback() error
+	Stats() map[string]interface{}
+	HasChanges() bool
+}
+
+type ChangeType string
+
+const (
+	ChangeFileCreated  ChangeType = "created"
+	ChangeFileModified ChangeType = "modified"
+	ChangeFileDeleted  ChangeType = "deleted"
+)
+
+type FileChange struct {
+	Path       string     `json:"path"`
+	Type       ChangeType `json:"type"`
+	SizeBefore int64      `json:"size_before,omitempty"`
+	SizeAfter  int64      `json:"size_after,omitempty"`
+	HashBefore string     `json:"hash_before,omitempty"`
+	HashAfter  string     `json:"hash_after,omitempty"`
+	Content    []byte     `json:"-"` // 回滚用原始内容，不参与 JSON 序列化
+}
+
+type ChangeSet struct {
+	ID        string       `json:"id"`
+	Action    string       `json:"action"`
+	Timestamp time.Time    `json:"timestamp"`
+	Files     []FileChange `json:"files"`
+}