Merges sexpr-activitypub-extension.md and sexpr-protocol-and-tiered-clients.md
into sexpr-unified-protocol.md — recognising that browsing, federation, and
real-time updates are all the same thing: peers exchanging s-expressions on
a bidirectional stream. One format, one connection, one parser.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
