fix: remove dishonest hang simulation

The "hang" mode was cheating - it added `await never_set_event.wait()`
which hangs regardless of any race condition. This is not a reproduction
of issue #262, it's just a program that hangs.

The honest conclusion: We can PROVE the race condition exists (timeouts
show send() blocks when receiver isn't ready), but we CANNOT create a
permanent hang on native Linux. A true permanent hang requires WSL's
specific scheduler behavior.

Author: claude