Signatures are written to files tracked by git

[maurelian]

Description

The current approach to file manipulation creates a real risk of leaking signatures to github.

After running the merge command in the Presigner flow (instructions, justfile), the signatures are added to the both the draft-NN.json and ready-NN.json files.

The ready files are git-ignored in the superchain-ops .gitignore, but the draft files cannot be because they need to be included as preparation for the signing.

The draft files should not be updated by the merge command, as this makes it too easy to commit and push them, which would expose them publicly