The landing page gains §3 Mail: a sender, two relays, and a recipient
exchange a real agent-mail/1.0 letter in the browser. A pure-JS HPKE
(X25519, HKDF-SHA256, ChaCha20-Poly1305, checked against the RFC 9180
known answer) reproduces the `original` and `reencrypted` vectors byte
for byte, then lets readers write their own letter, resend it via the
mirror (deduplicated by letter ID), or have a relay flip a ciphertext
byte or extend the header's expiry (both fail the AEAD tag and are
quarantined locally). A 7-step rail with a JSON/hexdump inspector and
the spec's three decisions explain each stage.

Mail, Knowledge, Discourse is now the order everywhere: sections, nav,
the stack diagram and cards, footer, hero lede, SDK matrix, and meta.
The hero stats add HPKE, the footer gains an Ecosystem column
(ICPanda DAO, dMsg, alink, Anda Bot), Chinese Mail terms follow the
spec, and the SDK grid no longer overflows on phones.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>