chore: add #[non_exhaustive] to remaining public structs (#768)

* chore: add #[non_exhaustive] to remaining public structs

* chore: add #[non_exhaustive] to remaining public types

* chore: enable exhaustive_structs/enums clippy lints

* test: add untagged ServerResult deserialization regression tests

crates/rmcp/tests/test_tool_builder_methods.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::exhaustive_structs)]
 //cargo test --test test_tool_builder_methods --features "client server macros"
 use rmcp::model::{JsonObject, Tool};
 use schemars::JsonSchema;