Adds NDR (Nostr Double Ratchet) as a channel extension providing
forward-secure E2E encrypted messaging over Nostr relays.
Features:
- Full channel implementation with send/receive/react
- Onboarding flow with invite URL acceptance and hello message
- Auto-generated identity if not configured
- Configurable relays (defaults to popular Nostr relays)
- Owner pubkey authentication for message filtering
Requires external `ndr` CLI (cargo install ndr).
Control surface: chat.iris.to
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
