Add Grace-Blackwell unified memory optimizations

Key changes based on HurbaLurba's DGX Spark research:

- Remove --gpu-only flag (fights unified memory fabric)
- Add --disable-pinned-memory, --force-fp16, --dont-upcast-attention
- Add CUDA env vars for unified memory: CUDA_MANAGED_FORCE_DEVICE_ALLOC,
  PYTORCH_NO_CUDA_MEMORY_CACHING, OMP_NUM_THREADS=20
- Document unified memory architecture best practices
- Add host-level GPU optimization instructions (clock locking, vboost)
- Document SageAttention PR #297 status (merged then reverted)
- Add credits section

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.example

@@ -9,7 +9,13 @@ SPARKYUI_DATA_PATH=/path/to/SparkyUI
 
 # ComfyUI settings
 COMFYUI_PORT=8188
-COMFYUI_FLAGS=--listen 0.0.0.0 --port 8188 --gpu-only
+
+# Optimized flags for Grace-Blackwell unified memory architecture
+# Key: DON'T use --gpu-only - it fights the unified memory fabric
+# --disable-pinned-memory: reduces overhead on unified fabric
+# --force-fp16 + --fp16-*: enables SageAttention optimization
+# --dont-upcast-attention: keeps attention in FP16 for speed
+COMFYUI_FLAGS=--listen 0.0.0.0 --port 8188 --disable-pinned-memory --force-fp16 --fp16-unet --fp16-vae --fp16-text-enc --dont-upcast-attention
 
 # Build refs (pin to specific commits/tags for reproducibility)
 COMFYUI_REF=master