fix(mcp-image-gen): fix HuggingFace authenticated download instructions

FLUX.1-schnell is a gated model — bare wget returns HTTP 401.

- Replace bare wget with huggingface-cli login + download (Option A)
- Add wget with Authorization header as Option B
- Add license acceptance prerequisite (huggingface.co gated repo)
- Add token creation link (huggingface.co/settings/tokens)
- Add fp8 quantized variant as alternative (~8.1GB, faster inference)
- Add download size note (~8GB, 10-30min)

mcp/mcp-image-gen/USAGE.md

@@ -27,11 +27,11 @@ The MCP server connects to ComfyUI's REST API at `http://localhost:8188`. If Com
 
 ### Install ComfyUI
 
-```bash
-# Option A — pip install (simplest)
-pip install comfyui
+> ⚠️ **ComfyUI is NOT on PyPI** — `pip install comfyui` will fail with "No matching distribution found".
+> It must be installed from source via `git clone`.
 
-# Option B — git clone (more control)
+```bash
+# Clone from source (the only correct installation method)
 git clone https://github.com/comfyanonymous/ComfyUI.git
 cd ComfyUI
 pip install -r requirements.txt
@@ -53,17 +53,48 @@ pip install torch torchvision --index-url https://download.pytorch.org/whl/rocm6
 
 FLUX.1-schnell is the recommended model — fast (4 steps), Apache 2.0 licensed, excellent quality.
 
-```bash
-# Download (~8GB) — place in ComfyUI/models/checkpoints/
-wget https://huggingface.co/black-forest-labs/FLUX.1-schnell/resolve/main/flux1-schnell.safetensors \
-     -O ~/ComfyUI/models/checkpoints/flux1-schnell.safetensors
+> ⚠️ **FLUX.1-schnell is a gated model on HuggingFace.**
+> A bare `wget` on the URL returns HTTP 401. You must:
+> 1. Accept the license at https://huggingface.co/black-forest-labs/FLUX.1-schnell (click **"Agree and access repository"** — one-time)
+> 2. Create a HuggingFace access token with **Read** permissions at https://huggingface.co/settings/tokens
 
-# Or use huggingface_hub:
+#### Option A — `huggingface-cli` (recommended)
+
+```bash
+# Install the HuggingFace Hub CLI
+pip install huggingface_hub
+
+# Log in — paste your Read token when prompted
+huggingface-cli login
+
+# Download (~8GB) directly into ComfyUI checkpoints
 huggingface-cli download black-forest-labs/FLUX.1-schnell \
     flux1-schnell.safetensors \
     --local-dir ~/ComfyUI/models/checkpoints/
 ```
 
+#### Option B — `wget` with Authorization header
+
+```bash
+wget --header="Authorization: Bearer hf_YOUR_TOKEN_HERE" \
+  https://huggingface.co/black-forest-labs/FLUX.1-schnell/resolve/main/flux1-schnell.safetensors \
+  -O ~/ComfyUI/models/checkpoints/flux1-schnell.safetensors
+```
+
+> Replace `hf_YOUR_TOKEN_HERE` with your actual HuggingFace token from https://huggingface.co/settings/tokens
+
+#### Alternative: fp8 quantized variant (~8.1GB, faster inference)
+
+If you want slightly faster inference with near-identical quality, the fp8 quantized version is also available:
+
+```bash
+huggingface-cli download black-forest-labs/FLUX.1-schnell-fp8 \
+    flux1-schnell-fp8.safetensors \
+    --local-dir ~/ComfyUI/models/checkpoints/
+```
+
+> **Download note:** Both variants are ~8GB — expect 10–30 minutes depending on connection speed.
+
 You'll also need the CLIP and VAE models — see the [ComfyUI FLUX guide](https://github.com/comfyanonymous/ComfyUI/blob/master/README.md) for full model list.
 
 ### Start ComfyUI (AMD ROCm)