repo create → init handoff is fragile

[angeloashmore]

The handoff between repo create and init --repo is error-prone.

repo create always generates a random 8-character domain (e.g. 7bcf54bf) and prints it in a human-readable message. init --repo needs that exact domain string.

Two problems observed in an agent test session:

1. repo create silently ignores positional arguments. Running prismic repo create my-repo-name doesn't warn that the positional was unused — the domain is still randomly generated. The agent assumed my-repo-name was the domain and passed it to init --repo, which then failed with "Repository not found."

2. The domain is only available in human-readable output. There's no --json flag on repo create to reliably capture the generated domain.

[angeloashmore]

As an alternative, we can combine the commands: automatically create a repo during init if a repo isn't provided.