Restart stale GUI and avoid port 8765 clash with fileShare

Old juc500_app processes kept serving pre-fix code; start.sh now
kills them and GUI defaults to port 8766.

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

start.sh

@@ -27,4 +27,23 @@ if ! "$PY" -c "import usb" 2>/dev/null; then
   exit 1
 fi
 
+# 이전 GUI 인스턴스 종료 (옛 코드가 포트 8765를 붙잡고 있으면 같은 에러가 반복됨)
+if command -v pgrep >/dev/null 2>&1; then
+  OLD_PIDS="$(pgrep -f "$ROOT/juc500_app.py" || true)"
+  if [[ -n "${OLD_PIDS}" ]]; then
+    echo "이전 JUC500 프로세스 종료: ${OLD_PIDS}"
+    # shellcheck disable=SC2086
+    kill ${OLD_PIDS} 2>/dev/null || true
+    sleep 0.4
+    # shellcheck disable=SC2086
+    kill -9 ${OLD_PIDS} 2>/dev/null || true
+  fi
+fi
+
+# 캐시된 .pyc 가 헷갈리지 않도록 (경량)
+rm -rf "$ROOT/juc500_xfer/__pycache__" 2>/dev/null || true
+
+REV="$("$PY" -c "from juc500_xfer import __version__; from juc500_xfer.usb_link import Juc500Link; print(__version__, 'backend_io=' + str(hasattr(Juc500Link, '_backend_bulk_write')))")"
+echo "JUC500 start — ${REV}"
+
 exec "$PY" "$ROOT/juc500_app.py" "$@"