feat(engine): implement self-reflection (reflector) stage in multi-agent pipeline

- Added ReflectorAgent for meta-cognition and critical review between Research and Writing
- Updated WriterAgent to explicitly address reflection critiques
- Introduced 'g1nation.enableReflection' configuration setting
- Added comprehensive integration tests for the self-reflection stage
- Documented design decisions in ADR-0010 and related discussion records

src/config.ts

@@ -67,6 +67,12 @@ export interface IAgentConfig {
      * Per-agent overrides live in AgentKnowledgeEntry.secondBrainWeight and win.
      */
     knowledgeMixSecondBrainWeight: number;
+    /**
+     * [Self-Reflection] Researcher와 Writer 사이에 메타인지 단계(Reflector)를 삽입할지 여부.
+     * true(기본): Reflector가 plan/research를 비판적으로 검토한 critique을 Writer에 주입.
+     * false: 기존 3단계(Planner→Researcher→Writer) 그대로 — 1 LLM 호출 절약 (저성능 모델/저지연 우선 시).
+     */
+    enableReflection: boolean;
 }
 
 // ─── 경로 정규화 유틸리티 ───
@@ -153,6 +159,7 @@ export function getConfig(): IAgentConfig {
         knowledgeMixSecondBrainWeight: Math.max(0, Math.min(100, Math.round(
             cfg.get<number>('knowledgeMix.secondBrainWeight', 50)
         ))),
+        enableReflection: cfg.get<boolean>('enableReflection', true),
     };
 }