Your manager represents the team, and represents the team whether they say "I" or "we". He can and should give you credit for your work at the appropriate time and place e.g. at your salary review and behind closed doors but the outside world couldn't care less who on your team came up with the demo. General Eisenhower gets full credit for the D-Day landings in Normandy but we all know that he never personally landed on those beaches. Nevertheless, the credit he gets is full and fully justifiable. Because he represents Team Allied.
You could escalate to your manager and your manager's manager but since your complaint is based on a non-understanding of management dynamics, you could pay anywhere from no price to a very stiff price for it. You could also call out your manager at the next meeting, but since your calling out is based on your non-understanding of management dynamics and since your calling out is very public, I surmise that the consequences may be most unpleasant for you.
Academia is a very different world, where faculty are in effect, individual research entrepreneurs. The department may get a nice rating from US News & World Report but the faculty does research as individuals and gets credit for their work as individuals. No matter how renowned the institution is, the institution is for all practical purposes just the place where they work. Note that in even in this case, faculty members are not in the habit of crediting the individual graduate student researchers on their team when they present the findings at conferences and seminars.
Good thing you restrained yourself and asked for advice before you act. How to handle it? That's up to you.
Clarification from the OP: "my manager not only took credit, but made claims implying that he had actually done the work (i.e., he made some decision while implementing code X for reason Y, he performed whatever testing, etc.) Saying "I had this demo developed", or even "I developed this demo" might be one thing; "I wrote these lines of code" seems different.
Well, your latest disclosure changes the nature of the beast. To put it bluntly, your manager lied outright. That's absolutely uncool. And I would count myself working for such a manager as a misfortune. If you are going to complain to your manager's manager, be sure to state SPECIFICALLY what he said. Your failure to be specific caused a miscommunication between you and me. You cannot afford such a miscommunication between you and your manager's manager. Your manager's offense was not in failing to give you credit but appropriating your work as his own. Doing that is known as stealing.
If you complain to your manager's manager, stress that you understand that a manager represents the team and is therefore entitled to use "we" and "I" in referring to the team's output. And that your complaint is about him appropriating your work as his own. Which is way different from representing the team. And the relief that you are seeking is that he stops doing that to you or anyone else on the team.