Pressing Disconnect with the instruments powered off froze the GUI
(apparent crash, 2026-07-06 15:52): worker.join(5) expired while the
worker sat in multi-second VISA timeouts, then bench.close() ran on the
GUI thread -- each driver close() first writes local() to the dead
device (stacked timeouts) and closing a session under an in-flight read
can also take NI-VISA down natively.
_disconnect now detaches the UI immediately and runs all instrument
teardown on a background thread; if the worker is still stuck in I/O
after a 15s join the sessions are deliberately left open (OS reclaims
them at exit) instead of being closed under a live read. Reconnecting
while a teardown is still releasing the instruments is refused with a
console hint.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
