core/tui: non-blocking MCP startup (#6334)

This makes MCP startup not block TUI startup. Messages sent while MCPs
are booting will be queued.


https://github.com/user-attachments/assets/96e1d234-5d8f-4932-a935-a675d35c05e0


Fixes #6317

---------

Co-authored-by: pakrym-oai <pakrym@openai.com>

codex-rs/core/src/tools/handlers/mcp_resource.rs

@@ -287,6 +287,8 @@ async fn handle_list_resources(
             let resources = session
                 .services
                 .mcp_connection_manager
+                .read()
+                .await
                 .list_all_resources()
                 .await;
             Ok(ListResourcesPayload::from_all_servers(resources))
@@ -396,6 +398,8 @@ async fn handle_list_resource_templates(
             let templates = session
                 .services
                 .mcp_connection_manager
+                .read()
+                .await
                 .list_all_resource_templates()
                 .await;
             Ok(ListResourceTemplatesPayload::from_all_servers(templates))

codex-rs/core/src/tools/router.rs

@@ -54,7 +54,7 @@ impl ToolRouter {
             .any(|config| config.spec.name() == tool_name)
     }
 
-    pub fn build_tool_call(
+    pub async fn build_tool_call(
         session: &Session,
         item: ResponseItem,
     ) -> Result<Option<ToolCall>, FunctionCallError> {
@@ -65,7 +65,7 @@ impl ToolRouter {
                 call_id,
                 ..
             } => {
-                if let Some((server, tool)) = session.parse_mcp_tool_name(&name) {
+                if let Some((server, tool)) = session.parse_mcp_tool_name(&name).await {
                     Ok(Some(ToolCall {
                         tool_name: name,
                         call_id,