8d6c8f7b

By: ValentinHirschi <valentin.hirschi@gmail.com>

move HEPKit graph integral ingress into native Vakint

Reuse native FeynKit routing and Symbolica operations with a thin typed Python boundary. Preserve explicit scalar substitutions, spectator routing and power validation.

Co-authored-by: Codex <noreply@openai.com>