style(server,agent): fmt + clippy fixes for Task 5 (CI green)

9082e11 compiles + passes all 50 server tests on the build host; only blocked
CI on cargo fmt (4 files) and one clippy -D dead-code denial:
- cargo fmt --all (relay/mod.rs, session/mod.rs, agent consent/mod.rs + session/mod.rs)
- #[cfg_attr(not(test), allow(dead_code))] on session::get_consent_state (a
  read accessor currently exercised only by tests)
No logic change.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

agent/src/session/mod.rs

@@ -533,15 +533,13 @@ impl SessionManager {
 
         // The MessageBox blocks the calling thread; run it on the blocking pool
         // so the agent's async loop is not stalled and heartbeats keep flowing.
-        let granted = tokio::task::spawn_blocking(move || {
-            prompt_consent(&technician_name, access)
-        })
-        .await
-        .unwrap_or_else(|e| {
-            // The blocking task panicked — fail closed (deny).
-            tracing::error!("Consent dialog task failed: {}; denying", e);
-            false
-        });
+        let granted = tokio::task::spawn_blocking(move || prompt_consent(&technician_name, access))
+            .await
+            .unwrap_or_else(|e| {
+                // The blocking task panicked — fail closed (deny).
+                tracing::error!("Consent dialog task failed: {}; denying", e);
+                false
+            });
 
         tracing::info!(
             "End user {} consent for session {}",