Adjust vLLM runtime defaults for local stack

Co-Authored-By: Oz <oz-agent@warp.dev>

.env.example

@@ -5,5 +5,12 @@ BACKEND_PORT=8000
 FRONTEND_PORT=3000
 HUGGINGFACE_CACHE_DIR=/home/${USER}/.cache/huggingface
 OPEN_WEBUI_DATA_DIR=./frontend/data/open-webui
-VLLM_MAX_MODEL_LEN=4096
-VLLM_GPU_MEMORY_UTILIZATION=0.88
+VLLM_MAX_MODEL_LEN=512
+VLLM_MAX_NUM_BATCHED_TOKENS=256
+VLLM_CHUNKED_PREFILL_FLAG=--enable-chunked-prefill
+VLLM_MAX_NUM_SEQS=1
+VLLM_GPU_MEMORY_UTILIZATION=0.7
+VLLM_DTYPE=bfloat16
+
+VLLM_ATTENTION_BACKEND=TRITON_ATTN
+HSA_OVERRIDE_GFX_VERSION=11.0.0