chore: add #[non_exhaustive] and mutation methods to improve compatibility (#715)

* chore: add #[non_exhaustive] to reduce backwards-incompatible changes going forward

* fix: remove ProtocolVersion import

* fix: add a few more with_ mutator methods

---------

Co-authored-by: Alex Hancock <alexhancock@block.xyz>

crates/rmcp/src/transport/streamable_http_client.rs

@@ -44,6 +44,7 @@ impl InsufficientScopeError {
 }
 
 #[derive(Error, Debug)]
+#[non_exhaustive]
 pub enum StreamableHttpError<E: std::error::Error + Send + Sync + 'static> {
     #[error("SSE error: {0}")]
     Sse(#[from] SseError),
@@ -81,12 +82,14 @@ pub enum StreamableHttpError<E: std::error::Error + Send + Sync + 'static> {
 }
 
 #[derive(Debug, Clone, Error)]
+#[non_exhaustive]
 pub enum StreamableHttpProtocolError {
     #[error("Missing session id in response")]
     MissingSessionIdInResponse,
 }
 
 #[allow(clippy::large_enum_variant)]
+#[non_exhaustive]
 pub enum StreamableHttpPostResponse {
     Accepted,
     Json(ServerJsonRpcMessage, Option<String>),