Padding of small Ethernet frames

Small Ethernet frames (i.e. smaller than 42/46 bytes) should perhaps be padded to the minimum frame length:

https://en.wikipedia.org/wiki/Ethernet_frame#Payload

Look for Ethernet frame handling in the codebase, likely in a module like `ethox::wire` or `ethox::layer`. Understand the current frame construction and where padding logic would be added. Check the Wikipedia link for Ethernet frame minimum length details (42/46 bytes). Write a test to verify small frames are padded correctly.

Rédigé par le modèle d'indexation à partir du texte de l'issue.