- Add double quotes to command so that the next argument isn't
  interpreted as the title for the start command.

- If the first argument is a valid path, convert it to Windows path
  notation. If `wslpath` fails—because it's a path from inside WSL,
  which cannot be converted to Windows path notation— fail with an
  error code.

  This last circumstance will show an error like so:

    wslpath: path: Result not representable