Fix potential crash during tool permission prompts: added optional chaining (?.) when accessing getAppState() and toolPermissionContext.mode in the permission request handler. Previously, if getAppState returned null or undefined (e.g., during teardown or an edge-case race condition), the application could throw a TypeError. The fix changes getAppState().toolPermissionContext.mode to getAppState?.()?.toolPermissionContext.mode, gracefully handling the null case. (search for "tengu_tool_use_show_permission_request" in function Qy at line ~573815)
