The '## CI minima' section claimed CI was optional and pointed to a
sample YAML, which is now wrong: real workflows live in .gitea/workflows/
and the missing piece is the runner registration, not the YAML.
New section covers:
- inventory of ci.yml + release.yml (matrix, trigger, concurrency)
- step-by-step act_runner registration with docker command
- egress to github.com requirement + mirror workaround
- pip cache key behaviour for the matrix
- tag pattern + manual v0.2.0 badge update checklist