87a8d9eb

By: Lucien Huber <im@lcnbr.ch>

move FeynKit workflows into native PyO3 API

User requests:
- There should be no Python facade functions; the API should all be PyO3 in FeynKit.
- Emit valid Linnest code and render diagrams through typst-py.
- Document all public classes, functions, methods, and meaningful accessors for particle physicists.
- Remove empty Parameters blocks and trivial accessor examples.
- Mark classes frozen where their public semantics are immutable.