Implements `scripts/agent/interop-test.mjs` to validate core Nostr operations
(Video Post, View Event, Encrypted DM) against a small set of public relays.
Ensures ephemeral keys are used and no private data is persisted.
Features:
- Ephemeral sender/receiver key generation.
- Polyfills for WebSocket, localStorage, and Crypto for Node.js environment.
- Verification of event signatures, IDs, and content shape.
- DM encryption/decryption roundtrip verification.
- Safe relay list usage (only 2 known relays).
