Fix after-transition video playback and click-triggered media behavior

[ErickWendel]

Summary

• Prevent videos from pausing after completed animation playback.
• Initialize imported and placeholder videos in a paused state.
• Preserve click-triggered playback until the user activates it.
• Expand unit and public-deck E2E coverage for playback state and triggers.

Testing

• Updated unit coverage for presenter playback persistence and imported video defaults.
• Updated editor media-controls E2E coverage for play/pause behavior.
• Added public-deck E2E coverage for after-transition and on-click video playback.