Remove Noise protocol references from wiki docs and tests

Delete 8 Noise-specific documentation pages (noise-xx.md,
transport-keys.md, adr-001/003/006, framing-codec.md) and update
~30 remaining wiki pages to reflect QUIC+TLS as the sole transport.
Remove obsolete Noise-based integration tests (auth_service.rs,
mls_group.rs). Code-side Noise removal was done in f334ed3.

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

docs/src/cryptography/identity-keys.md

@@ -138,26 +138,6 @@ The Ed25519 public key bytes (`public_key_bytes()`) are used as the
 KeyPackages indexed by this key, and the Delivery Service routes messages to
 queues indexed by the same key.
 
-## Distinction from the X25519 Noise Keypair
-
-It is critical to understand that the Ed25519 identity key and the X25519
-transport key are **separate keys on different curves serving different
-purposes**:
-
-| Property | Ed25519 Identity Key | X25519 Noise Key |
-|----------|---------------------|-----------------|
-| Curve | Twisted Edwards (Ed25519) | Montgomery (Curve25519) |
-| Operation | Digital signatures | Diffie-Hellman key exchange |
-| Purpose | MLS credentials, AS registration | Noise\_XX mutual authentication |
-| Lifetime | Permanent (per client) | Per server process or per connection |
-| Persistence | Serialized to state file | Not serialized (M6 deferred) |
-| Source | `identity.rs` | `keypair.rs` |
-
-Although both curves are related (Curve25519 is birationally equivalent to
-Ed25519's curve), the keys are **not interchangeable**. Converting between them
-requires explicit birational mapping, which quicnprotochat intentionally avoids
-to maintain clean separation of concerns.
-
 ## Serialization
 
 `IdentityKeypair` implements `Serialize` and `Deserialize` (serde) by
@@ -193,7 +173,6 @@ is deterministically re-derived on load.
 ## Related Pages
 
 - [Cryptography Overview](overview.md) -- algorithm inventory
-- [X25519 Transport Keys](transport-keys.md) -- the other keypair
 - [Key Lifecycle and Zeroization](key-lifecycle.md) -- full lifecycle diagram
 - [Post-Compromise Security](post-compromise-security.md) -- how MLS credentials interact with PCS
 - [Threat Model](threat-model.md) -- what identity keys protect and do not protect