feat: add protocol comparison docs, P2P crate, production audit, and design fixes

Add comprehensive documentation comparing quicnprotochat against classical
chat protocols (IRC+SSL, XMPP, Telegram) with diagrams and attack scenarios.
Promote comparison pages to top-level sidebar section. Include P2P transport
crate (iroh), production readiness audit, CI workflows, dependency policy,
and continued architecture improvements across all crates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/quicnprotochat-core/src/opaque_auth.rs

@@ -14,9 +14,7 @@ pub struct OpaqueSuite;
 
 impl CipherSuite for OpaqueSuite {
     type OprfCs = opaque_ke::Ristretto255;
-    type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDh<
-        opaque_ke::Ristretto255,
-        sha2::Sha512,
-    >;
+    type KeyExchange =
+        opaque_ke::key_exchange::tripledh::TripleDh<opaque_ke::Ristretto255, sha2::Sha512>;
     type Ksf = argon2::Argon2<'static>;
 }