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/src/handler/server/common.rs

@@ -138,6 +138,7 @@ where
     }
 }
 
+#[expect(clippy::exhaustive_structs, reason = "intentionally exhaustive")]
 pub struct Extension<T>(pub T);
 
 impl<C, T> FromContextPart<C> for Extension<T>
@@ -182,6 +183,7 @@ where
     }
 }
 
+#[expect(clippy::exhaustive_structs, reason = "intentionally exhaustive")]
 pub struct RequestId(pub crate::model::RequestId);
 
 impl<C> FromContextPart<C> for RequestId