Use browser tests to screenshot the most important use cases

We can use use browser tests to screenshot the most important use cases and add that as automatic documentation.

It would be nice to do even a small part of these ideas. This ticket can be split also.

- [ ] As a first step let's just make sure the screenshots from a whole pass of browser tests are valid and output the best and most descriptive ones to somewhere like `/docs/screenshots` folder.
- [ ] The names of the screenshots should be relevant (the current naming is ok for test debugging but we can make a new copy for each sensible image with a descriptive and relevant name. Sequence numbers could be useful to order the screenshots.
- [ ] Consider saving a separate Markdown file that links to the screenshots or use plain folder view of GitHub.
- [ ] Consider if we could have the screenshots from `/manual` be automated. Perhaps with some or no markings on the screenshots.

Start by running a complete browser-test pass and inspect the screenshots it produces. Check how the current debugging-oriented names are generated, then determine which images are valid and descriptive enough to copy or expose under /docs/screenshots. Done means the selected screenshots are available with relevant names, with any Markdown index treated as a separate follow-up.

Written by the indexing model from the issue text.