1. Typography: install @tailwindcss/typography and add to plugins so prose
classes render correctly in article/about/legal templates.
2. Callout block: fix icon branches to match CalloutBlock.ICON_CHOICES
(info/warning/trophy/tip). Previous template branched on error/success
which are unreachable; info fell through to else silently.
3. Nav newsletter feedback: remove 'hidden' class from desktop nav
data-newsletter-message element. JS sets textContent only; hidden
class prevented message from ever being visible.
4. Popular Articles sidebar: add numbered Popular Articles widget to home
page sidebar matching wireframe, using latest_articles context with
alternating cyan/pink number accents and read_time_mins.
Rebuild CSS: typography plugin grows output from 24KB to 47KB.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
