feat: prompt returns answer to caller + commit on own header line

crates/common/src/protocol.rs

@@ -137,6 +137,8 @@ pub enum ClientMessage {
     },
     /// Response to a clipboard-get request
     ClipboardGetResponse { request_id: Uuid, text: String },
+    /// Response to a prompt request — contains the user's typed answer
+    PromptResponse { request_id: Uuid, answer: String },
 }
 
 /// Mouse button variants