Make workflows and jobs conditional: - Full QA / lint runs if source files change. - QA / Test runs if source files change. - The Spread workflow calls the `test/**` Spread tests if source files change. Add a Docs Spread workflow that runs the `docs/**` Spread tests if docs files change. With the QA workflow, if there's a change to the source, all linters run in one runner (`make lint`). But for the Spread tests, there's a hard split between the docs and source Spread tests, meaning each will spawn their own runner. This isn't bad, but it adds complexity and inconsistency between the different workflow types. If Starflow's QA workflow were completely split, we could properly partition the checks in both collections – QA source, QA docs, Spread source, Spread docs. --- - [x] I've followed the [contribution guidelines](https://github.com/canonical/rockcraft/blob/main/CONTRIBUTING.md). - [x] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [x] I've successfully run `make lint && make test`. - [ ] I've added or updated any relevant documentation. - [ ] In documents I changed, I [added a meta description](https://canonical-starflow.readthedocs-hosted.com/how-to/add-a-page-meta-description/) if one was missing. - [ ] I've updated the relevant release notes.