CI flow tooling

Provide tooling/examples/documentation to use `edgly` in a CI flow:

- automatically create fiddles from new branches/PRs and link to fiddle in PR comment
- some way to pull in fiddle changes back into PR, e.g. via checkbox click in the PR comment (but ensure only users with write access to code can do this)
- deploy to stage and run tests on PR commits
- deploy to prod and run tests on main commits
- regularly run prod tests via CI as health monitoring

Start by reviewing the edgly CLI and any existing documentation or examples for CI usage. Define the CI workflow for branches and pull requests, staging, production, and scheduled health checks, including how fiddle changes return to a PR and how write access is enforced. Done means each requested flow is documented or supported and its permissions and test execution are demonstrated.

Written by the indexing model from the issue text.