ch-go migration - phase 2

We already use ch-go for encoding and decoding. There are other places we can potentially utilize it - specifically proto calls such as handshakes.

Start by tracing the proto calls involved in handshakes and identify where encoding and decoding are still separate from the existing ch-go usage. Review those handshake paths first, then determine the relevant completion checks for migrating them to ch-go and verify the affected proto calls.

Written by the indexing model from the issue text.