fix: api ergonomics follow-up (#720)

* fix: builder with_* methods take T instead of Option<T>

* fix: emit conditional builder calls for optional fields in macros

* fix: convert with_task, with_stop_reason, with_logger, with_content to proper builders

* fix: update test callers for new builder signatures

* fix: simplify make_task helper and remove unused import

* fix: update sampling_stdio example for new with_stop_reason signature

* fix: make annotations and execution Option<Expr> consistent with other fields

* fix: remove unused none_expr import

crates/rmcp/tests/test_task_support_validation.rs

@@ -13,7 +13,6 @@ use rmcp::{
     model::{CallToolRequestParams, ClientInfo, ErrorCode, JsonObject},
     tool, tool_handler, tool_router,
 };
-use serde_json::json;
 
 /// Server with tools having different task support modes.
 #[derive(Debug, Clone)]
@@ -75,8 +74,8 @@ impl ClientHandler for DummyClientHandler {
 }
 
 /// Helper to create a task object for tool calls
-fn make_task() -> Option<JsonObject> {
-    Some(json!({}).as_object().unwrap().clone())
+fn make_task() -> JsonObject {
+    serde_json::Map::new()
 }
 
 #[tokio::test]