Runtime modes

Foreground, background, and manual

• exo.run_forever() runs on the current thread.
• exo.run_background() starts an SDK-owned background thread.
• exo.update() advances one step from an existing loop.

exo.start();
exo.run_background();
// application work
exo.request_stop();
exo.join();
exo.close();

Do not combine runtime drivers. UpdateResult reports the tick, executed task count, and whether another task exists. stop() stops the domain; use ExoDevice::start()/stop() only for independent multi-device control.