Move _logs_since_flush reset outside the callback loop so all
registered callbacks receive the same log data instead of only
the first callback getting logs while subsequent ones get an empty list.
Add test to verify multiple callbacks all receive the same logs.
When running ComfyUI in API mode on Windows, print() statements from
custom nodes can crash with "OSError: [Errno 22] Invalid argument"
during flush. This occurs because piped/redirected stdout streams on
Windows may fail to flush even after successful writes.
This fix catches OSError with errno 22 (EINVAL) specifically in
LogInterceptor.flush(), allowing the flush callbacks to still execute.
The error is safe to ignore since write() already succeeded.
Fixes#11367