docs(research): add inference engine, spec decoding and multi-GPU research

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/research/README.md

@@ -27,6 +27,7 @@ Each file here is a **dated snapshot**: research or a decision record as it stoo
 | [proxy-request-priority.md](proxy-request-priority.md) | Superseded by the OmniRoute migration | Priority tiers via LiteLLM's scheduler, never built on OmniRoute |
 | [proxy-shadow-pricing.md](proxy-shadow-pricing.md) | Superseded by the OmniRoute migration | Shadow cost was wired into LiteLLM config, and nothing implements it now |
 | [proxy-tool-choice.md](proxy-tool-choice.md) | Superseded by the OmniRoute migration | Chose LiteLLM. It mentions Open WebUI, which has been removed |
+| [inference-engine-spec-decoding-multi-gpu.md](inference-engine-spec-decoding-multi-gpu.md) | Current | llama.cpp vs. vLLM vs. SGLang on R9700: drafters, multi-GPU, licenses, `--cache-ram` misspelling bug. Not benchmarked |
 | [qwen3.8-27b-quant.md](qwen3.8-27b-quant.md) | Current | Main model quant and VRAM budget |
 | [qwen3.8-27b-throughput-tuning.md](qwen3.8-27b-throughput-tuning.md) | Current | Tokens/s tuning from the server log, DDR RAM as a cache tier, comparison with five outside R9700 configs. Proposals only, nothing applied |
 | [qwen3.8-27b-tool-calling.md](qwen3.8-27b-tool-calling.md) | Current | Tool-calling parser risk for the main model |