Introducing Playgroups

TCGCore's structure changed in a big way: playgroups are now the top-level thing you create and invite friends to, and a format is just a ruleset — set pool, banlist, rotation — that a playgroup can link to. That means a single playgroup can now mix and match: link the official Standard/Pioneer/Modern/Legacy/Pauper/Commander formats alongside your own custom set-pool format, all under one roof with shared membership, decks, matches, and stats. Custom formats are public by default and show up in a new "Browse formats" page, so you can link someone else's format read-only, or copy it into your own editable version.