When window.nostr isn't available (common on mobile Chrome where
extensions can't inject), fall back to NIP-55 nostrsigner: intent
URIs. This opens Amber/Primal directly to sign a NIP-98 event,
then redirects back with the signed event for JWT authentication.
- Build nostrsigner: URI with unsigned NIP-98 event + callback URL
- Process NIP-55 callback on page mount (extract signed event from URL)
- Auto-detect Android to show "SIGN IN WITH AMBER / PRIMAL" label
- Reduced window.nostr polling from 3s to 2s before NIP-55 fallback
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
