Show matched interests as a tag row instead of a callout

With the why line gone the accent-bar callout held nothing but "Matches: a · b",
which no longer earned its quoting. Every surface now puts one row directly
under the rubric: a small-caps "Matches" label and one pill chip per interest.
On the web that is one `.interest-chip` component (admins still get links to
the interest's article filter); the EPUB gets `.matches`/`.interest` rules in
both stylesheets, and `Understanding::interests_line` goes.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ESJbbzQ1b8fs5AA65tKw2q

src/web/tailwind.css

@@ -186,6 +186,8 @@
 
   .reader-page :where(h1, h2, h3, h4), .reader-section-heading { text-wrap:balance; }
   .reader-section-heading { @apply border-t-[3px] border-double border-rule-strong pt-3 font-serif text-[1.05rem] font-semibold uppercase leading-[1.2] tracking-[0.15em] text-ink; }
+  .interest-chip { @apply inline-block rounded-full border border-rule-strong px-2.5 py-0.5 text-xs leading-5 text-ink-2 no-underline; }
+  a.interest-chip:hover { @apply border-accent text-accent; }
 
   .rating { @apply my-5 flex flex-wrap items-center gap-x-3 font-sans text-xs; }
   .rating-prompt { @apply font-serif text-[0.8rem] italic text-muted; }