fix: resolve clippy redundant_closure and expand env vars in socket field

CI sets RUSTFLAGS=-D warnings which promotes redundant_closure to an
error. Also apply substitute_env_vars to the socket field so configs
like socket: "$ENVOY_SOCK" resolve correctly, matching how uri and
headers are already handled.

Author: wpfleger96

crates/goose/src/agents/extension_manager.rs

@@ -729,7 +729,7 @@ impl ExtensionManager {
                     self.client_name.clone(),
                     capability,
                     &effective_working_dir,
-                    socket.as_deref(),
+                    socket.as_ref().map(|s| substitute_env_vars(s, &all_envs)).as_deref(),
                 )
                 .await?
             }

crates/goose/src/agents/unix_socket_http_client.rs

@@ -85,7 +85,7 @@ async fn connect_unix(socket_path: &str) -> Result<UnixStream, std::io::Error> {
             Ok::<_, std::io::Error>(stream)
         })
         .await
-        .map_err(|e| std::io::Error::other(e))??;
+        .map_err(std::io::Error::other)??;
         return UnixStream::from_std(std_stream);
     }