fix: run_forever() now waits for thread completion before returning (closes #152)

[botbikamordehai2-sketch]

What

run_forever() was polling self.terminated in a loop and could return before the websocket's closed() method had finished executing. This is because client_terminated and server_terminated are set to True in websocket.py before closed() is called, so self.terminated returns True prematurely.

Fix

Instead of polling self.terminated, run_forever() now simply calls self._th.join() which blocks until the worker thread has fully completed — including after closed() returns. This is simpler, more correct, and avoids the race condition entirely.

Closes #152