Addresses the trust gap where a hub relay can forward media from
unknown relays without the receiving relay's consent. Introduces
delegate=true flag on [[trusted]] entries: when set, the relay
accepts media forwarded through the trusted peer from relays it
vouches for. Without delegate, only direct media is accepted.
Covers: FederationTrustChain signal, origin authorization checks,
TTL for chain depth limiting, anti-spam properties. 5 phases, ~3 days.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>