fix(server::peers::operator::auth): make ChallengeContext pub for smlang state machine

smlang generates a public state enum whose variants contain ChallengeContext,
requiring the type itself to be fully public. Also tightens the wildcard arm
in client auth to an exhaustive match.

server/crates/arbiter-server/src/peers/client/auth.rs

@@ -298,7 +298,7 @@ where
 
     let signature = expect_message(transport, |req: Inbound| match req {
         Inbound::AuthChallengeSolution { signature } => Some(signature),
-        _ => None,
+        Inbound::AuthChallengeRequest { .. } => None,
     })
     .await
     .map_err(|e| {

server/crates/arbiter-server/src/peers/operator/auth/state.rs

@@ -14,19 +14,19 @@ use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl};
 use diesel_async::RunQueryDsl;
 use tracing::error;
 
-pub(super) struct ChallengeRequest {
+pub(crate) struct ChallengeRequest {
-    pub(super) pubkey: authn::PublicKey,
+    pub(crate) pubkey: authn::PublicKey,
-    pub(super) bootstrap_token: Option<String>,
+    pub(crate) bootstrap_token: Option<String>,
 }
 
-pub(super) struct ChallengeContext {
+pub struct ChallengeContext {
-    pub(super) challenge: AuthChallenge,
+    pub challenge: AuthChallenge,
-    pub(super) pubkey: authn::PublicKey,
+    pub pubkey: authn::PublicKey,
-    pub(super) bootstrap_token: Option<String>,
+    pub bootstrap_token: Option<String>,
 }
 
-pub(super) struct ChallengeSolution {
+pub(crate) struct ChallengeSolution {
-    pub(super) solution: Vec<u8>,
+    pub(crate) solution: Vec<u8>,
 }
 
 smlang::statemachine!(
@@ -127,8 +127,6 @@ where
         })
     }
 
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
     async fn verify_solution(
         &mut self,
         ChallengeContext {