ask_operator tool: non-blocking; operator answer arrives as helper event

new mcp tool on the manager surface that queues a question on the
dashboard and returns the question id immediately. operator submits an
answer via /answer-question/<id>; the dashboard fires
HelperEvent::OperatorAnswered { id, question, answer } into the manager
inbox so the next turn picks it up.

also: fix async-form button stuck on spinner after successful submit
(refreshState skipped re-rendering, so the button was never re-enabled).

hive-c0re/src/main.rs

@@ -15,6 +15,7 @@ mod coordinator;
 mod dashboard;
 mod lifecycle;
 mod manager_server;
+mod operator_questions;
 mod server;
 
 use coordinator::Coordinator;