feat: add local feature for !Send tool handler support (#740)

* feat: add local feature for !Send tool handler support

* fix: gate streamable HTTP transport on not(local) feature

crates/rmcp/src/service/client.rs

@@ -162,7 +162,8 @@ impl<S: Service<RoleClient>> ServiceExt<RoleClient> for S {
         self,
         transport: T,
         ct: CancellationToken,
-    ) -> impl Future<Output = Result<RunningService<RoleClient, Self>, ClientInitializeError>> + Send
+    ) -> impl Future<Output = Result<RunningService<RoleClient, Self>, ClientInitializeError>>
+    + MaybeSendFuture
     where
         T: IntoTransport<RoleClient, E, A>,
         E: std::error::Error + Send + Sync + 'static,

crates/rmcp/src/service/server.rs

@@ -95,7 +95,8 @@ impl<S: Service<RoleServer>> ServiceExt<RoleServer> for S {
         self,
         transport: T,
         ct: CancellationToken,
-    ) -> impl Future<Output = Result<RunningService<RoleServer, Self>, ServerInitializeError>> + Send
+    ) -> impl Future<Output = Result<RunningService<RoleServer, Self>, ServerInitializeError>>
+    + MaybeSendFuture
     where
         T: IntoTransport<RoleServer, E, A>,
         E: std::error::Error + Send + Sync + 'static,

crates/rmcp/src/service/tower.rs

@@ -3,7 +3,7 @@ use std::{future::poll_fn, marker::PhantomData};
 use tower_service::Service as TowerService;
 
 use super::NotificationContext;
-use crate::service::{RequestContext, Service, ServiceRole};
+use crate::service::{MaybeSendFuture, RequestContext, Service, ServiceRole};
 
 pub struct TowerHandler<S, R: ServiceRole> {
     pub service: S,
@@ -44,7 +44,7 @@ where
         &self,
         _notification: R::PeerNot,
         _context: NotificationContext<R>,
-    ) -> impl Future<Output = Result<(), crate::ErrorData>> + Send + '_ {
+    ) -> impl Future<Output = Result<(), crate::ErrorData>> + MaybeSendFuture + '_ {
         std::future::ready(Ok(()))
     }