feat: converge dynamic plugins onto canonical homeagent-sdk

- Separate built-in plugin interface from external plugin interface
- Route dynamic plugin loading through homeagent-sdk/sdk using reflection
- Turn internal/sdk into an enhanced wrapper over canonical SDK types
- Vendor SDK repo snapshot under third_party/homeagent-sdk for stable builds
- Keep internal constructors/adapters for memory, knowledge, llm, settings
- Align dynamic QQ loading with canonical SDK chain

internal/sdk/llm.go

@@ -1,42 +1,29 @@
 package sdk
 
-import agentAPI "gitcode.com/JianFeeeee/HomeAgent/internal/agent/api"
+import (
+	sdkext "gitcode.com/JianFeeeee/homeagent-sdk/sdk"
+	agentAPI "gitcode.com/JianFeeeee/HomeAgent/internal/agent/api"
+)
 
-type LLMAPI interface {
-	ListSources() []string
-	SetSource(name string) error
-	CurrentSource() string
-}
+type LLMAPI = sdkext.LLMAPI
 
-type llmImpl struct {
-	mgr *agentAPI.ProviderManager
-}
+type llmImpl struct{ mgr *agentAPI.ProviderManager }
 
-func NewLLM(mgr *agentAPI.ProviderManager) LLMAPI {
-	return &llmImpl{mgr: mgr}
-}
+func NewLLM(mgr *agentAPI.ProviderManager) LLMAPI { return &llmImpl{mgr: mgr} }
 
 func (l *llmImpl) ListSources() []string {
-	if l.mgr == nil {
-		return nil
-	}
+	if l.mgr == nil { return nil }
 	return l.mgr.List()
 }
 
 func (l *llmImpl) SetSource(name string) error {
-	if l.mgr == nil {
-		return nil
-	}
+	if l.mgr == nil { return nil }
 	return l.mgr.SetDefault(name)
 }
 
 func (l *llmImpl) CurrentSource() string {
-	if l.mgr == nil {
-		return ""
-	}
+	if l.mgr == nil { return "" }
 	p := l.mgr.Default()
-	if p == nil {
-		return ""
-	}
+	if p == nil { return "" }
 	return p.Name()
 }