docs: add missing #[must_use], # Errors, # Panics across public api

hive-ag3nt/src/web_ui.rs

@@ -75,6 +75,9 @@ impl AppState {
 /// `post_compact`) the allowed-tools surface claude sees.
 pub type Flavor = mcp::Flavor;
 
+/// # Errors
+///
+/// Returns an error if the TCP listener cannot bind to the given port.
 pub async fn serve(
     label: String,
     port: u16,