Add Graph/RAG adapter matrix coverage

[yvette-carlisle]

Summary

• add the XY-1071 RAGFlow, GraphRAG, and LightRAG adapter matrix rows for retrieval, citation, navigation, stale-source behavior, answer faithfulness, and knowledge compilation
• add a durable JSON/Markdown evidence report and README/index links
• preserve typed non-pass boundaries: 0 pass rows and no graph/RAG parity or generic RAG-platform claim

Validation

• cargo make real-world-memory-graph-rag
• cargo nextest run -p elf-eval --test real_world_job_benchmark external_adapter_run_summarizes_nonzero_scenario_losses generated_json_report_renders_markdown
• cargo make checks

Decodex recovery note

• Decodex lane XY-1071 lost usable lifecycle ownership after repo-gate validation failed and then misattributed liveness to the long-running decodex serve process. This PR was manually recovered with the same XY-1071 authority after full local validation passed.