Create workspace

Create a new Docsbook documentation site (workspace) — the FIRST call for 'make a docs site', 'set up documentation', «сделай документацию». Idempotent: a repository that already has a workspace is returned with already_existed: true, so no lookup is needed first. Pages come next: write_docs, which takes MANY files in one call, so a whole first site lands as one commit. Ask docsbook_expert what the site should contain before writing it. GITHUB IS OPTIONAL — this is the tool for BOTH cases: • From scratch, no GitHub at all: OMIT repo_full_name. Docsbook creates and hosts the documentation repository itself, under its own GitHub organisation, with its own credentials. The user needs no GitHub account, no connected GitHub app and no repository — never tell them to connect GitHub or bring a repo for this. Then call write_docs to publish the pages you wrote. • From the user's OWN repository: pass repo_full_name ('owner/repo'). Use this when they point at a repository of theirs — including the git remote of the checkout they are working in, which counts as pointing at it — it is what the site READS and what its address is made of, so it must be a repository that exists on GitHub. A repository GitHub does not have, or that Docsbook cannot see, is created as a Docsbook-hosted site instead, and the result then reports a different repo_full_name than you asked for. If a workspace for this repo already exists, returns the existing one (already_existed: true). ALWAYS give the user site_url from the result verbatim; never build a link out of a GitHub username or repo name.