fix: resolve live stream chat cross-platform visibility

[barrydeen]

Summary

• Fix dedup race condition: The live-chat-discovery and live-chat-{dTag} subscriptions both receive kind 1311 events but only one copy passed the relay pool dedup check. When discovery won the race, the event went to trackChatter() (pill counts only) instead of addChatMessage() — silently dropping the message from chat. Registered "live-chat-" as a dedup bypass prefix so both subs independently reach EventRouter.
• Fix ephemeral relay fragility: Chat relay connections were created with write=false and autoReconnect=false, meaning they couldn't survive transient drops during long streams. Now created with write=true, autoReconnect=true and released on cleanup.
• Remove stale clearSeenEvents() call that was a workaround for the dedup issue and unnecessarily flushed the entire pool's seen-event cache.

Test plan

• Open a live stream and verify chat messages from other clients appear in real time
• Send a chat message and verify it appears on other Nostr clients (e.g. Amethyst, Coracle)
• Stay in a stream for 5+ minutes and verify messages continue arriving (no silent disconnect)
• Leave and re-enter a stream — verify chat loads correctly
• Verify LiveNowRow pill chatter counts still update on the feed screen