fix: re-open panel when childIssues changes to prevent stale sub-task list

Add childIssues to the useEffect dependency array so the Properties panel
is refreshed whenever the child issue list updates (e.g. an agent creates
or deletes a sub-task while the panel is open). Previously the panel kept
the snapshot from the initial render of the parent issue.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/pages/IssueDetail.tsx

@@ -989,7 +989,7 @@ export function IssueDetail() {
       );
     }
     return () => closePanel();
-  }, [issue]); // eslint-disable-line react-hooks/exhaustive-deps
+  }, [issue, childIssues]); // eslint-disable-line react-hooks/exhaustive-deps
 
   const inboxQuickArchiveArmedRef = useRef(false);
   const canQuickArchiveFromInbox =