Use spec-as-source-setup to add spec-as-source enforcement to this project.

Project state:

• tessl init has already been run
• tessl-labs/spec-driven-development is already installed
• The git repo is initialized (git init done)
• No scripts/ directory exists yet
• No .pre-commit-config.yaml exists
• No .github/workflows/ directory exists
• The project uses pytest

After creating all files, ask the user which test runner to use before finalising the CI workflow, show the post-setup checklist, then run spec-verify.