feat: CMS-editable nav, categories taxonomy, site settings

- Move top nav from hugo.toml menus to data/nav.yml (CMS-editable)
- Add categories taxonomy alongside tags
- Add Decap CMS settings collection for nav management
- Add categories field to articles and essays in CMS config

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

site/hugo.toml

@@ -7,37 +7,11 @@ title = 'ASW — Agentic Semantic Web'
 
 [taxonomies]
   tag = "tags"
+  category = "categories"
 
-# ── Navigation menus ──────────────────────────────────────────────────
-[[menus.main]]
-  name = "Home"
-  url  = "/"
-  weight = 1
-
-[[menus.main]]
-  name = "Docs"
-  url  = "/docs/"
-  weight = 2
-
-[[menus.main]]
-  name = "Notes"
-  url  = "/notes/"
-  weight = 3
-
-[[menus.main]]
-  name = "Essays"
-  url  = "/essays/"
-  weight = 4
-
-[[menus.main]]
-  name = "Articles"
-  url  = "/articles/"
-  weight = 5
-
-[[menus.main]]
-  name = "Tags"
-  url  = "/tags/"
-  weight = 6
+# ── Navigation ──────────────────────────────────────────────────────
+# Top nav is driven by data/nav.yml (editable via Decap CMS).
+# Docs sidebar is auto-generated from content/docs/ subdirectories.
 
 # ── Docs sidebar ─────────────────────────────────────────────────────
 # Auto-generated from content/docs/ subdirectories.