Add an option to opt out of YouTube Watch Together

[theg1239]

Feature request

Add an option for a participant to opt out of YouTube Watch Together.

Motivation

A meeting participant may want to remain in the call without participating in the shared YouTube viewing experience.

Proposed behavior

Provide a clear control that lets an individual participant disable or leave YouTube Watch Together without leaving the meeting.

Acceptance criteria

• Participants can opt out of YouTube Watch Together independently.
• Opting out does not disconnect the participant from the meeting.
• The control is easy to find from the Watch Together experience.