- Extend SkateCrew with `sponsorRef` (sponsoring shop, NIP-15 stall coord) and
`coordinator` (Cordn/MLS encrypted-chat Delivery Service pointer), plus parser.
- CrewSponsorBanner: "Sponsored by [Shop]" banner that resolves and links the
backing shop; renders nothing if the shop can't be resolved.
- CrewCoordinatorCard: surfaces the crew's private-chat coordinator (E2E · MLS),
explains what the coordinator can/can't see, shows the operator, and prompts
the leader to set one up when absent — the UI foundation for Cordn chat.
- Wire the sponsor banner (under hero) and coordinator card (sidebar) into
CrewDetailPage.
- CrewForm: add "Sponsored by" and "Private Chat Coordinator" inputs with
validation; publish `sponsor` and `coordinator` tags.
- NIP.md: document the `sponsor` and `coordinator` tags, the structured invite
kind 36229 (with accept/decline flow), and the Cordn/MLS private-chat model
and why it's the chosen fit for crews.
Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>
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