Feature-complete SVG import and rendering support

Graphite is a powerful graphics editor, but it currently struggles to handle complex SVG files perfectly. Important details like custom text styles or advanced shapes may sometimes get lost when opening or saving files. My goal is to fix this by building a reliable, complete SVG pipeline. Firstly, I plan to add missing core features like gradients, patterns, and a proper Text-on-Path node so that Graphite can edit more SVG artwork natively. Followed by this, for any highly complex SVG features that Graphite still would not be able to edit directly, I will build a fallback system. This system will automatically convert those unsupported parts into static images rather than silently dropping them, ensuring the artwork looks exactly right when opened. Finally, I will improve how Graphite exports files, making sure layer names are saved as clean SVG IDs. Altogether, these changes will make Graphite a tool that artists can fully trust for professional SVG work.