feat: editor write path

features/article_title_rules.qa.md

@@ -73,6 +73,15 @@ Package: `test` (black-box, alongside `article_test.go` / `use_case_baseline_tes
     article\n"` -- regression proof a non-title failure still answers 500.
 14. `POST /v1/article/` with no jwt cookie -> status `401` (regression: the route is
     still gated).
+15. `PATCH /v1/article/1` with a cookie of a user holding content.update and a title of
+    2 / 3 / 200 / 201 ASCII characters -> `400` unchanged / `200` stored / `200` stored /
+    `400` unchanged. Body `apperr.ArticleTitleErrorMessage + "\n"` on the 400s.
+16. `PATCH /v1/article/1` with `"title": ""` (present but empty) -> `400`, title unchanged
+    (guard against `omitempty` on a `*string` skipping validation).
+17. Configure the fake repo so its next `Update` returns `article.ErrInvalidTitle`.
+    `PATCH /v1/article/1` with title "Valid Title" -> `400`, body
+    `apperr.ArticleTitleErrorMessage + "\n"`.
+18. `PATCH /v1/article/1` with only a new title -> `200`, slug unchanged.
 
 ## Manual verification (not exercised by the Go test)
 - None. This slice has no SPA-visible behaviour and no SMTP involvement.