Rockcraft generates slash-separated extension part names for Ubuntu 22.04/24.04 and dot-separated names for Ubuntu 26.04 and higher. The 12-factor documentation previously showed only the older syntax, which led to invalid `rockcraft.yaml` customizations for newer bases and paas-charm projects. This updates the framework references and web-app guides with synchronized base tabs and concrete `extension/part` versus `extension.part` guidance. It also documents the Ubuntu 26.04 Flask and Django `app-image` resource name, updates generated profile comments, and keeps the profile snapshots aligned. Validation: - focused `sphinx-lint` checks - full Sphinx dummy build with warnings treated as errors - `pytest -q tests/unit/test_cli.py` (7 passed) - pre-commit hooks --- - [ ] I've followed the [contribution guidelines](https://github.com/canonical/rockcraft/blob/main/CONTRIBUTING.md). - [ ] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [ ] 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.