Add news posts with banner summaries on the home page

Posts live in content/post/; the five latest are summarised on the home
page. Builds for check/deploy go to build/ so they do not collide with a
running hugo server writing to public/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDRjtmAiNpo5mK5N3d7QwZ

hugo.toml

@@ -6,6 +6,10 @@ disableKinds = ["rss", "sitemap"]
 # pages keep working when the site is served from a sub-directory
 relativeURLs = true
 
+# a post named 2026-10-11-my-title.md gets its date from the file name (and the URL /post/my-title/)
+[frontmatter]
+  date = ["date", ":filename", ":default"]
+
 [params]
   description = "The Old-Computers.com museum of computers, consoles and pongs, rebuilt from the Wayback Machine archive."
 
@@ -21,6 +25,10 @@ relativeURLs = true
   collection = "collections"
 
 [menus]
+  [[menus.main]]
+    name = "News"
+    pageRef = "/post"
+    weight = 5
   [[menus.main]]
     name = "Museum"
     pageRef = "/museum"