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/comments-demo/index.php

@@ -0,0 +1,59 @@
+<?php
+
+// Demonstrates attaching Lib\Comments to a page — see /admin/docs/comments.
+// This is the one post under App/pages/blog/ with a sidecar, specifically
+// so it can carry a live comment thread; giving it one is what excludes
+// it from the static HTML cache (Renderer::render() only ever caches
+// sidecar-less pages) — every other post stays sidecar-less/cached and
+// has no thread, since blog/_layout/layout.twig only includes one when
+// 'comments' is present in the returned context.
+
+use App\AdminAuth;
+use App\Response;
+use Lib\Comments;
+use Lib\Csrf;
+use Lib\FormValidator;
+use Lib\Input;
+use Lib\SpamGuard;
+
+$pagePath = Comments::currentPagePath();
+$user = AdminAuth::currentUser();
+$spamGuard = new SpamGuard();
+$commentError = null;
+
+if ($_SERVER['REQUEST_METHOD'] === 'POST') {
+    if (!Csrf::verify(Input::post('csrf_token'))) {
+        return Response::redirect($pagePath . '?error=security');
+    }
+
+    if ($user === null) {
+        return Response::redirect($pagePath . '?error=login');
+    }
+
+    $body = Input::post('body', '');
+    $validator = (new FormValidator())
+        ->required($body, 'body', 'Enter a comment.')
+        ->maxLength($body, 'body', 2000, 'Comments are 2000 characters max.');
+
+    if ($validator->passes()) {
+        // Same "bot gets an identical response" reasoning as the contact
+        // form — see App/pages/contact/index.php. Only the insert is
+        // skipped for spam.
+        if (!$spamGuard->isSpam(Input::post())) {
+            Comments::create($pagePath, $user['id'], $body);
+        }
+
+        return Response::redirect($pagePath);
+    }
+
+    $commentError = $validator->errors()['body'] ?? null;
+}
+
+return [
+    'comments'     => Comments::forPage($pagePath),
+    'currentUser'  => $user,
+    'commentError' => $commentError,
+    'renderedAt'   => $spamGuard->renderedAt(),
+    'csrfField'    => Csrf::fieldName(),
+    'csrfToken'    => Csrf::token(),
+];

App/pages/blog/comments-demo/index.twig

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+{% extends layout %}
+
+{% import '_layout/icons.twig' as icons %}
+
+{% block title %}Comments Demo{% endblock %}
+{% block description %}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.{% endblock %}
+
+{% block robots %}index, follow{% endblock %}
+{% block tags %}comments, meta{% endblock %}
+{% block canonical %}{{ request_path|default('/') }}{% endblock %}
+
+{% block og_type %}article{% endblock %}
+{% block og_title %}{{ block('title') }}{% endblock %}
+{% block og_description %}{{ block('description') }}{% endblock %}
+{% block og_url %}{{ block('canonical') }}{% endblock %}
+
+{% block twitter_card %}summary{% endblock %}
+{% block twitter_title %}{{ block('title') }}{% endblock %}
+{% block twitter_description %}{{ block('description') }}{% endblock %}
+
+{% block blog_content %}
+    <h1>Comments Demo</h1>
+
+    <p>Unlike every other post under <code>App/pages/blog/</code>, this one has its own <code>index.php</code> sidecar — <code>App/pages/blog/comments-demo/index.php</code> — which reads and writes a <code>comments</code> table via <code>Lib\Comments</code> and returns a <code>comments</code> key in its context. <code>App/pages/blog/_layout/layout.twig</code> only includes the comment-thread partial (<code>novaconium/pages/_partials/comments/thread.twig</code>) when that key is present, so this is the only post here with a thread below.</p>
+
+    <p>Having a sidecar means this page is never served from the static HTML cache the way its sidecar-less siblings are (see <a class="icon-link" href="/admin/docs/caching">{{ icons.book() }}Static caching</a>) — an explicit, per-page tradeoff you accept the moment a page needs comments. See <a class="icon-link" href="/admin/docs/comments">{{ icons.users() }}Comments</a> for the full write-up of <code>Lib\Comments</code>, including why comments are tied to real logged-in accounts rather than anonymous name/email fields, and why they're auto-approved with after-the-fact moderation at <code>/admin/comments</code> rather than a pending queue.</p>
+{% endblock %}