Could not install with the current method suggested in Readme. Removing --index-url works.

Ran with `pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/cu126`

```
Discarding https://download.pytorch.org/whl/typing_extensions-4.12.2-py3-none-any.whl#sha256=04e5ca0351e0f3f85c6853954072df659d0d13fac324d0072316b67d7794700d (from https://download.pytorch.org/whl/cu126/typing-extensions/): Requested typing-extensions>=4.10.0 from https://download.pytorch.org/whl/typing_extensions-4.12.2-py3-none-any.whl#sha256=04e5ca0351e0f3f85c6853954072df659d0d13fac324d0072316b67d7794700d (from torch) has inconsistent Name: expected 'typing-extensions', but metadata has 'typing_extensions'
ERROR: Could not find a version that satisfies the requirement typing-extensions>=4.10.0 (from torch) (from versions: 4.4.0, 4.8.0, 4.9.0, 4.12.2)
ERROR: No matching distribution found for typing-extensions>=4.10.0
WARNING: There was an error checking the latest version of pip.
```

Without --index-url it works, at least on my installation (I installed a ton of AI stuff there, who knows what pulls what from where).

Here's my whole process under Arch Linux (with python3 downgraded to python3.10) in a venv:

```
git clone https://github.com/lllyasviel/FramePack.git
cd FramePack
python3 -m venv venv
source venv/bin/activate
pip install torch torchvision torchaudio
pip install -r requirements.txt
python demo_gradio.py --server 192.168.x.x --port 8000
```

Start with the installation command in the README and the dependencies listed in requirements.txt. Reproduce the reported command in a Python 3.10 virtual environment on Arch Linux, compare it with the command that omits --index-url, and check whether the documented setup completes without the typing-extensions error.

Written by the indexing model from the issue text.