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/config.go

@@ -0,0 +1,10 @@
+package sdk
+
+import "gitcode.com/JianFeeeee/HomeAgent/pkg/types"
+
+// ConfigAPI provides read/write access to the runtime config object
+// (unrelated to the config database).
+type ConfigAPI interface {
+	Get() *types.Config
+	Put(cfg *types.Config)
+}