Show what the pipeline understood about each article

A muted one-line note now follows every article: the deep assessment's
topic group, format, depth and technicality, the specific topics it
extracted, and the reader interests the article matched best, e.g.

  Software engineering · analysis essay · in depth · highly technical ·
  Topics: copy-on-write, ZFS · Interests: Filesystems, Rust

It renders on the web article page footer, on the public and private
issue-page entries, in the EPUB article footer and in the EPUB "In This
Issue" index (both editions), always styled like the existing meta lines
so it stays secondary to the content.

`Pick` gains `top_interests` (serde default, no migration), filled from
the signals stage when the editor assembles the lineup; the facets were
already on the issue snapshot via `Pick.llm`, so earlier issues show the
facet and topic parts and only future issues carry interests. One shared
builder, `understanding_line` in epub::chapters, feeds every surface.

The dev seed gives four picks facets and interests so the line can be
eyeballed locally.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QVPagF6jfDv78CC5Jv2wp4

src/web/templates/issue_public.html

@@ -4,6 +4,6 @@
   <header class="mb-10 text-center"><p class="font-sans text-[0.72rem] uppercase tracking-[0.12em] text-muted">{{ issue.display_date }} · No. {{ issue.issue_number }}</p><p class="mt-2 font-sans text-sm text-muted">{{ issue.stats_line }}</p><p class="mx-auto mt-5 max-w-[58ch] text-lg italic leading-relaxed text-ink-2">A personal morning paper, assembled daily; the selection is the reader's, the words are the authors'.</p></header>
   <p class="notice mb-8"><a href="/login">Sign in</a> to read every article's full text and download the editions, or <a href="/request-access">request access</a>.</p>
   {% if !downloads.is_empty() %}<div class="mb-8 flex flex-wrap justify-center gap-2">{% for download in downloads %}<a class="btn" href="{{ download.href }}">{{ download.label }} <span class="ml-1 text-muted">{{ download.size }}</span></a>{% endfor %}</div>{% endif %}
-  {% for section in issue.sections %}<section class="mt-14"><h2 class="reader-section-heading">{{ section.name }}</h2><div>{% for entry in section.entries %}<article class="border-b border-rule py-6{% if entry.is_lead %} pt-5{% endif %}"><h3 class="font-semibold leading-[1.1] tracking-[-0.01em] {% if entry.is_lead %}text-3xl{% else %}text-2xl{% endif %}"><a class="text-ink no-underline hover:text-accent" href="{{ entry.url }}">{{ entry.title }}</a></h3><p class="mt-2 font-sans text-sm leading-relaxed text-muted">{% match entry.author %}{% when Some with (author) %}{{ author }} · {% when None %}{% endmatch %}{{ entry.source }}{% if !entry.domain.is_empty() %} ({{ entry.domain }}){% endif %} · {{ entry.reading_minutes }} min</p>{% match entry.summary %}{% when Some with (summary) %}<p class="index-summary mt-4">{{ summary }}</p>{% when None %}{% endmatch %}{% match entry.why %}{% when Some with (why) %}<p class="mt-4 border-l-2 border-accent pl-3 italic text-ink-2">Why it's here: {{ why }}</p>{% when None %}{% endmatch %}{% if !entry.comment_links.is_empty() %}<p class="mt-3 flex flex-wrap gap-x-4 gap-y-1 font-sans text-sm text-muted">{% for link in entry.comment_links %}<a class="text-muted hover:text-accent" rel="noopener" target="_blank" href="{{ link.url }}">{{ link.label }}{% if !link.meta.is_empty() %}: {{ link.meta }}{% endif %}</a>{% endfor %}</p>{% endif %}</article>{% endfor %}</div></section>{% endfor %}
+  {% for section in issue.sections %}<section class="mt-14"><h2 class="reader-section-heading">{{ section.name }}</h2><div>{% for entry in section.entries %}<article class="border-b border-rule py-6{% if entry.is_lead %} pt-5{% endif %}"><h3 class="font-semibold leading-[1.1] tracking-[-0.01em] {% if entry.is_lead %}text-3xl{% else %}text-2xl{% endif %}"><a class="text-ink no-underline hover:text-accent" href="{{ entry.url }}">{{ entry.title }}</a></h3><p class="mt-2 font-sans text-sm leading-relaxed text-muted">{% match entry.author %}{% when Some with (author) %}{{ author }} · {% when None %}{% endmatch %}{{ entry.source }}{% if !entry.domain.is_empty() %} ({{ entry.domain }}){% endif %} · {{ entry.reading_minutes }} min</p>{% match entry.summary %}{% when Some with (summary) %}<p class="index-summary mt-4">{{ summary }}</p>{% when None %}{% endmatch %}{% match entry.why %}{% when Some with (why) %}<p class="mt-4 border-l-2 border-accent pl-3 italic text-ink-2">Why it's here: {{ why }}</p>{% when None %}{% endmatch %}{% match entry.understanding %}{% when Some with (line) %}<p class="mt-3 font-sans text-sm text-muted">{{ line }}</p>{% when None %}{% endmatch %}{% if !entry.comment_links.is_empty() %}<p class="mt-3 flex flex-wrap gap-x-4 gap-y-1 font-sans text-sm text-muted">{% for link in entry.comment_links %}<a class="text-muted hover:text-accent" rel="noopener" target="_blank" href="{{ link.url }}">{{ link.label }}{% if !link.meta.is_empty() %}: {{ link.meta }}{% endif %}</a>{% endfor %}</p>{% endif %}</article>{% endfor %}</div></section>{% endfor %}
   <p class="mt-10 text-center font-sans text-sm"><a href="/issues">Browse the archive →</a></p>
 {% endif %}</article>{% endblock %}