Many docs make passing reference to core24 as the default base. This PR updates the tutorials and how to guides to core26. **Exceptions** 12-factor tutorials have been left out, as agreed. Following discussion in the ticket ROCKCRAFT-294, the following are also excluded: - [Chisel a rock](https://documentation.ubuntu.com/rockcraft/latest/how-to/chiselling/chisel-existing-rock/) is already updated in the draft PR. However, the purpose seems to be the same as the tutorial [Shrink a rock with Chisel](https://documentation.ubuntu.com/rockcraft/latest/tutorial/chisel/). As the how-to is already quite detailed, the tutorial will be removed in a future PR. - [Create a package slice for Chisel](https://documentation.ubuntu.com/rockcraft/latest/how-to/chiselling/create-slice/) will be removed as it duplicates content in Chisel. Metadata descriptions were added to all edited documentation pages. --- - [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`. - [x] I've added or updated any relevant documentation. - [x] 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.