feat: flagship native client, fast and local-first

[sepehr-safari]

Scope

The flagship native client: a fast, local-first Nostr client. A polished, focused vertical slice first, depth over breadth.

Built on the nostr library and its local-first store; signs via Signet (NIP-46) or a local key. Development lives in the zig-nostr/plaza repo.

The pillars

1. Onboarding under two minutes. Browse with no key; when the user wants to post, generate a key or connect Signet (invisible key management); smart default relays and a curated starter pack so the feed is never empty.
2. Local-first performance. The feed renders from the local store instantly and reconciles from relays in the background; optimistic posting; progressive relay fanout that never blocks on the slowest relay.

Client basics

Single-column feed, compose and post, follow and unfollow, profile view (kind:0), NIP-65 outbox.