Endless buffering when seeking while paused

Chunks are not remuxed when seeking while the media is paused. We need to subscribe to seek events of the video element instead of only relying on timeupdate events.

Start by locating the video element handlers for seek and timeupdate events, then trace how paused seeking triggers chunk remuxing and buffering. Confirm the fix by reproducing a seek while paused and verifying that remuxing runs and playback no longer buffers endlessly.

Written by the indexing model from the issue text.