feat: Phase 6.1 收尾 — 目的路由接入所有AI组件

- Orchestrator 现在接受独立的 chatAdapter 和 intentAdapter
- BackgroundThinker 使用 deep_thinking purpose 适配器
- MemoryExtractor 使用 memory_extraction purpose 适配器
- Synthesizer 使用 chat purpose 适配器
- .env 回退时所有适配器共享同一 provider，完全向后兼容

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/ai-core/internal/orchestrator/orchestrator.go

@@ -70,11 +70,13 @@ func (o *Orchestrator) getBus() bus.Bus {
 	return o.eventBus
 }
 
-// NewOrchestrator 创建编排器
+// NewOrchestrator 创建编排器。
+// chatAdapter 用于对话生成 (PurposeChat)，intentAdapter 用于意图分析 (PurposeIntentAnalysis)。
 func NewOrchestrator(
 	personaLoader *persona.Loader,
 	contextBuilder *ctxbuild.Builder,
-	llmAdapter *llm.Adapter,
+	chatAdapter *llm.Adapter,
+	intentAdapter *llm.Adapter,
 	subManager *subsession.Manager,
 	memoryRetriever *memory.Retriever,
 	memoryExtractor *memory.Extractor,
@@ -82,10 +84,10 @@ func NewOrchestrator(
 	return &Orchestrator{
 		personaLoader:   personaLoader,
 		contextBuilder:  contextBuilder,
-		llmAdapter:      llmAdapter,
+		llmAdapter:      chatAdapter,
 		subManager:      subManager,
-		intentAnalyzer:  NewIntentAnalyzer(llmAdapter),
-		synthesizer:     NewSynthesizer(llmAdapter),
+		intentAnalyzer:  NewIntentAnalyzer(intentAdapter),
+		synthesizer:     NewSynthesizer(chatAdapter),
 		memoryRetriever: memoryRetriever,
 		memoryExtractor: memoryExtractor,
 	}