chore: groundwork for sites & authors

docs/design/sites-authors-slices.md

@@ -0,0 +1,29 @@
+# Sites and authors: cross-slice context
+
+The design for Sites and Authors is in `screens/sites.md`, `screens/authors.md`, the "Editor: site and authors", "Profile: author profile" and "Articles: sites and authors" sections of the editor, profile and articles docs, and the board groups listed in `README.md` (pass 3). Behaviour still comes from `features/`; where the two disagree, stop and ask.
+
+## Roles
+| Action | Owner | Admin | Other roles |
+|---|---|---|---|
+| Create, edit, set default, delete a site | yes | no | no |
+| Read the site list, choose an article's site | yes | yes | yes, if they can edit the article |
+| Create, edit, delete any author | yes | yes | no |
+| Read authors, pick authors on an article | yes | yes | yes |
+| Create and edit their own linked author (`POST /v1/author/me`) | yes | yes | yes |
+| Create an author from the editor ("Create author…", "This is me") | yes | yes | no |
+
+## Decisions already taken
+- One site per article (`site_id` on the article). No per-site publish state: `is_online` stays the global switch. API keys stay global.
+- The site key is immutable after creation. Exactly one default site exists and it cannot be deleted. Deleting a site with articles requires `reassign_to`.
+- Authors are separate from users. An optional, unique link to a user. The slug is globally unique and not tied to a site. Zero authors on an article is allowed and never blocks publishing. Deleting an author with articles requires `reassign_to` (an author id or `none`).
+- Media used as an author avatar or a site's default social image counts as media usage.
+- The default site is seeded once from `PUBLIC_URL`. That variable is the CMS's own address (email links), so the seed is only a starting value that the owner edits. The base URL must be https, except for loopback hosts.
+- Existing articles are backfilled to the default site and get no authors.
+
+## Slices, in order
+1. Sites API. 2. Authors API (independent of 1; both touch the article update route and the article response, so merge 1 first and rebase 2).
+3. Sites and Authors screens plus the shared directory pieces (`DirectoryFrame.dc.html`). Existing Editor, Articles and Profile screens are not changed here.
+4. Editor, Articles and Profile integration, which also makes every existing frame of those screens pass the visual check.
+
+## Open point for the first slice
+`PATCH /v1/article/{id}` is served by `UpdateArticleBody` and only updates the body. Extending it with `site_id` and `author_ids[]` or splitting a metadata endpoint is decided in the specifier step of slices 1 and 2.