Uses the existing gift-wrap primitive (kind 14 rumor, one p-tag per recipient):
- useGroupConversations: lists multi-recipient threads, bucketed by the sorted
participant key; the inbox shows a Groups section
- GroupConversationPage (/messages/group/:participants): encrypted group thread
with sender names, send + error feedback
- smoke test now boots the new route
Group creation UI (multi-select in NewMessageDialog) is the next step. For
stronger guarantees (forward secrecy, rosters) Marmot/MLS or Cordn would be the
protocol to adopt later; noted in the hook.
New /leaderboards route (linked from the More menu): aggregates kind-9735
receipts into top-zapped spots and top supporters, with week/month/all-time
tabs. Reuses the batched zap helpers. Also hardens the deploy smoke test to
boot lazy routes (/, /leaderboards, /bounties), since route chunks can fail
independently.
