style(blog): add section dividers + drop redundant presenter comment

Code-quality reviewer flagged stylistic divergence from auth's pattern:
- All 3 blog use cases now have // ── Input ──... / ── Output ──... /
  ── Use case ──... section dividers (consistent with auth Task 3 + plan
  template §4.1).
- Removed inline comment in get-articles controller's presenter that
  appeared in only 1 of 3 controllers; identity presenters are
  self-explanatory.

packages/blog/src/interface-adapters/controllers/get-articles.controller.ts

@@ -6,7 +6,6 @@ import {
 } from "../../application/use-cases/get-articles.use-case";
 
 function presenter(value: GetArticlesOutput) {
-  // identity for now (R11 — every non-void controller has a presenter)
   return value;
 }