Unfortunately, I do not have access to the video transcript for the presentation "AWS re:Invent 2025 - Zoom's Journey from Conversation to Completion with AI Companion 3.0 (ISV321)". Without the transcript, I am unable to provide a detailed summary as requested. If you are able to share the transcript or a recording of the presentation, I would be happy to analyze the content and provide a comprehensive summary in the requested Markdown format. Please let me know if you can provide the necessary materials.