How would you cite the Hansard in AMA?

This is how I would cite it based on the Australian Government's Style Manual (which is a Harvard style) and the AMA's guidelines for a "government or agency bulletin". For the PDF, you would need to add the URL and the dates you accessed it:

1. Senate of Australia. Parliamentary Debates: Senate Official Hansard. Canberra, Australia: Commonwealth of Australia; 2016. No. 5, 2016. http://parlinfo.aph.gov.au/parlInfo/download/chamber/hansards/1ea904ea-ae93-4f0c-bb20-3d8c33e83f81/toc_pdf/Senate_2016_03_17_4198_Official.pdf. Accessed April 13, 2016.

Watch the URL for this - you don't want to include the fileType= stuff at the end that you get from copying and pasting from the website.

This is working on the assumption that you were trying to cite the PDF of the whole Hansard, which is the simplest and easiest thing to do.  You can access pieces of the Hansard online, but quite frankly the Parliament hasn't provided good details on their website to use for a citation.  Since you can cite the PDF, you may as well.

Keep in mind that I'm writing this in April, 2016.  By the time you feel the need to use it, some things may have changed.