feat: standardize resource-not-found error code (SEP-2164) (#899)

* feat: implement SEP-2164 resource not found errors

* test: update protocol version utility expectations

* feat: gate not-found code at server boundary

---------

Co-authored-by: Michael Neale <michael.neale@gmail.com>

conformance/src/bin/server.rs

@@ -615,7 +615,7 @@ impl ServerHandler for ConformanceServer {
                 } else {
                     Err(ErrorData::resource_not_found(
                         format!("Resource not found: {}", uri),
-                        None,
+                        Some(json!({ "uri": uri })),
                     ))
                 }
             }