Add JSON-RPC interface and refactor for MCP support

src/tick.rs

@@ -291,11 +291,15 @@ pub async fn run_tick_engine(state: SharedState) {
                     return None;
                 }
                 let conn = st.players.get(&pid)?;
-                Some((
-                    conn.channel,
-                    conn.handle.clone(),
-                    format!("{}{}", msg, ansi::prompt()),
-                ))
+                if let (Some(ch), Some(h)) = (conn.channel, &conn.handle) {
+                    Some((
+                        ch,
+                        h.clone(),
+                        format!("{}{}", msg, ansi::prompt()),
+                    ))
+                } else {
+                    None
+                }
             })
             .collect();