feat!: add MRTR behavior support (SEP-2322) (#929)

* feat!: add MRTR behavior support

* feat: harden SEP-2322 MRTR support

* ci: diff public API only on features common to base and head

cargo public-api builds both revisions with the same feature set, so a
feature introduced (or removed) by a PR broke the build of the other
revision. Restrict the all-features diff to features present in both the
base and head revisions.

crates/rmcp-macros/src/tool_handler.rs

@@ -47,7 +47,7 @@ pub fn tool_handler(attr: TokenStream, input: TokenStream) -> syn::Result<TokenS
                 &self,
                 request: rmcp::model::CallToolRequestParams,
                 context: rmcp::service::RequestContext<rmcp::RoleServer>,
-            ) -> Result<rmcp::model::CallToolResult, rmcp::ErrorData> {
+            ) -> Result<rmcp::model::CallToolResponse, rmcp::ErrorData> {
                 let tcc = rmcp::handler::server::tool::ToolCallContext::new(self, request, context);
                 #router.call(tcc).await
             }