Add GPU Lab configs, docs, and runbooks for VM303.

Mirror gpu-lab compose files and model-manager catalog from GPU-Dev; document Dockhand mapping and SGLang cutover target.

README.md

@@ -1,3 +1,35 @@
-# atc-GPU
+# atc-GPU — GPU Lab Infrastructure
 
-GPU Lab infrastructure — VM303 model-manager, gpu-lab Docker stacks, Dockhand
+Infrastructure-as-code and documentation for the ATC GPU Lab environment on **VM303 (GPU-Dev)**.
+
+## Quick links
+
+| Service | URL |
+|---------|-----|
+| GPU Lab UI | http://10.0.20.106:9000/ |
+| Inference API (active runtime) | http://10.0.20.106:8010/v1/models |
+| OpenAI gateway | http://10.0.20.106:8001/v1/models |
+| Dockhand (GPU-Dev env) | http://atc-docker01.dell-atc.lan:8082/ |
+
+## Repository layout
+
+```
+atc-GPU/
+├── README.md
+├── docs/           # Landscape, models, runbooks, Dockhand mapping
+├── config/         # gpu-lab compose + model-manager catalog (no secrets)
+├── compose/        # Dockhand-safe compose variants
+└── scripts/        # Helper scripts (activate-model)
+```
+
+## Active target (2026-06)
+
+- **Runtime:** SGLang (`sglang-modern`) via `compose.sglang.yml`
+- **Model:** Qwen 3.6 27B AWQ (`qwen36-27b-awq` → served as `qwen3.6-27b-awq`)
+- **Previous:** Llama3-70b-GPTQ on vLLM legacy (to be decommissioned after cutover)
+
+See [docs/runbook-vm303.md](docs/runbook-vm303.md) for activate/rollback steps.
+
+## Related repos
+
+- [mo/Lakehouse](http://atc-mgt01.dell-atc.lan:3001/mo/Lakehouse) — Spark, Trino, Debezium, Airflow, S3 pipeline