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

package.json

@@ -411,6 +411,11 @@
           "minimum": 0,
           "maximum": 100,
           "description": "Knowledge Mix (0–100): how heavily the assistant should lean on Second Brain evidence vs. its own general knowledge. 0 = Second Brain disabled (model knowledge only). 50 = balanced (legacy default). 100 = Second Brain is the primary evidence; model knowledge only fills harmless background. Per-agent overrides in the Agent Mapping panel win over this global value."
+        },
+        "g1nation.enableReflection": {
+          "type": "boolean",
+          "default": true,
+          "description": "Insert a Self-Reflection (Reflector) stage between Researcher and Writer in the multi-agent workflow. The Reflector critically reviews the plan and research output (gaps, contradictions, unsupported claims, drift from the original objective) and feeds a structured critique to the Writer, which must address it before producing the final report. Reflection failures are non-fatal (the Writer still runs with empty critique). Disable to save one LLM call per mission if you prioritize latency or are running on a very small model."
         }
       }
     }