Docs Restructuring, Contribution Templates, and Evaluation Rubric

Take steps to make docs more accessible.

## Related

#4072

## Acceptance Criteria

* [x] new Guides section on Gitbook
* [x] group related sections together in Gitbook into meaningful sections
* [x] introduce a content type taxonomy `concept, task, reference, tutorial`
* [x] templates for each content type
* [x] update installation guide
* [ ] add tags to gitbook and begin apply
* [ ] add job story new issue template to github, review bug template
* [ ] style guideline / 1 pager
* [ ] run / develop a script or skill to identify / apply page tags
* [ ] clear new tags (run after each release)
* [ ] flag to rewrite if it has screenshots
* [ ] delete pages flagged to delete (run before each release)
* [x] designate a page status e.g. `flag to delete, flag to rewrite, new` and apply
*

* rubric to evaluate existing articles
* Does title match the content type? (task = verb phrase)
* Can user tell within 10 seconds what doc is for?
* Are all steps testable as written?
* Is audience clear (developer, policy author, registry admin)?
* Are there broken links or stale screenshots?
*

## Artifacts

| Type | Purpose | Example |
| --- | --- | --- |
| `concept` | What it is / why it exists | Standard Registry overview, TrustChain, Architecture |
| `task` | How to do one thing | Configure MFA, Import schema from Excel |
| `reference` | Complete spec, scannable | API endpoints, Schema fields, CLI flags |
| `tutorial / guide` | End-to-end scenario | Demo Guide, VM0033 Workthrough |