Remove placeholder install script URLs from documentation

[Copilot]

The installation documentation referenced a non-existent script at https://install.fsl-continuum.sh, which would cause errors for users attempting the quick start.

Changes

• Removed all "Quick Setup with Installer" sections referencing the placeholder URL
• Updated quick start examples to use the working installation method:

# Before (broken)
curl -sSL https://install.fsl-continuum.sh | bash

# After (working)
git clone https://github.com/swcstudio/fsl-continuum.git
cd fsl-continuum
pip install -r requirements.txt
pip install -e .

Files Modified

• README-new.md
• docs/0001-getting-started/README.md
• docs/0001-getting-started/0002-quick-start.md
• docs/0001-getting-started/0003-installation.md

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.