新增实例槽位隔离与结构化日志，多开不再共用日志与账号

internal/instance/lock_windows.go

@@ -0,0 +1,43 @@
+//go:build windows
+
+package instance
+
+import (
+	"errors"
+
+	"golang.org/x/sys/windows"
+)
+
+type windowsInstanceLock struct {
+	handle windows.Handle
+}
+
+// tryAcquireInstanceLock 用共享模式为 0 的 CreateFile 独占锁文件：
+// 已被占用的锁文件会返回 ERROR_SHARING_VIOLATION，此时调用方继续扫描下一个槽位。
+func tryAcquireInstanceLock(path string) (instanceLock, bool, error) {
+	handle, err := windows.CreateFile(
+		windows.StringToUTF16Ptr(path),
+		windows.GENERIC_READ|windows.GENERIC_WRITE,
+		0,
+		nil,
+		windows.OPEN_ALWAYS,
+		windows.FILE_ATTRIBUTE_NORMAL,
+		0,
+	)
+	if err != nil {
+		if errors.Is(err, windows.ERROR_SHARING_VIOLATION) || errors.Is(err, windows.ERROR_ACCESS_DENIED) {
+			return nil, false, nil
+		}
+		return nil, false, err
+	}
+	return &windowsInstanceLock{handle: handle}, true, nil
+}
+
+func (l *windowsInstanceLock) Close() error {
+	if l == nil || l.handle == windows.InvalidHandle {
+		return nil
+	}
+	err := windows.CloseHandle(l.handle)
+	l.handle = windows.InvalidHandle
+	return err
+}