Multi-relay support

[kwsantiago]

Problem

Currently whisper connects to a single relay. If that relay is down or slow, the operation fails.

Solution

Accept multiple relay URLs and publish/subscribe to all of them.

Send behavior

• Publish to all relays in parallel
• Success if any relay accepts
• Report which relays succeeded/failed in verbose mode

Recv behavior

• Subscribe to all relays
• Deduplicate incoming messages by event ID
• Graceful handling when relays disconnect

Interface

# Multiple --relay flags
whisper send --relay wss://relay1.example --relay wss://relay2.example ...

# Or comma-separated
whisper send --relays wss://relay1.example,wss://relay2.example ...

# Environment variable
export NOSTR_RELAYS="wss://relay1.example,wss://relay2.example"

Implementation Notes

• Use libwebsockets multi-connection support
• Track event IDs in a small hash set for dedup (recv)
• First-success-wins for send, all-parallel for recv