Add in-house comments (Lib\Comments)

A reusable comment thread any sidecar can attach to any page, tied to
real logged-in accounts (never anonymous), auto-approved on submission
with hide/delete moderation at /admin/comments — only a verified account
can post, so there's no anonymous-spam vector to pre-vet against.

Framework-level (novaconium/lib, novaconium/migrations, novaconium/pages),
not App/migrations, matching Admin auth and Media manager's shape. A page
needs its own sidecar to use it — this repo has no client-side JS, so
comments ride the same server-rendered POST pattern as every other
dynamic feature, which is also what excludes a page from the static
cache. App/pages/blog/comments-demo/ demonstrates the pattern without
touching existing posts that are referenced elsewhere as the
sidecar-less example.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

App/pages/blog/index.php

@@ -46,5 +46,11 @@ return [
             'excerpt'   => 'A tour of what ships with novaconium out of the box: routing, sidecars, caching, admin auth, access control, media manager, database, search, RSS, and more.',
             'published' => '2026-07-15',
         ],
+        [
+            'slug'      => 'comments-demo',
+            'title'     => 'Comments Demo',
+            'excerpt'   => 'A worked example of Lib\\Comments — this post has its own sidecar, unlike every other post here, specifically so it can carry a live comment thread.',
+            'published' => '2026-07-15',
+        ],
     ],
 ];