Fix missing _is_not_supported and harden WinUSB config cache

Restores the helper accidentally removed when adding access-denied
handling, retries I/O after seeding pyusb config index on Windows, and
handles USB overflow reads without crashing the HELLO loop.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/setup_macos.sh

@@ -20,7 +20,9 @@ pip install --no-index --find-links=vendor/wheels -r requirements.txt \
 pip install -e .
 
 echo
-echo "설치 완료. 예:"
+echo "설치 완료. 실행:"
+echo "  ./start.sh"
+echo "예:"
 echo "  source $ROOT/.venv/bin/activate"
 echo "  juc500 info"
 echo "  juc500 gui"