feat(player): show video stats icon in theatre mode

[dcmclarke]

Proposed changes

Resolves #1162

Video stats icon was only rendered in the stream info bar below the video, which is hidden in theatre mode. This made the stats inaccessible for users who exclusively use theatre mode.

Fix adds theatre mode detection in PlayerStreamInfo.vue using a MutationObserver that watches for the persistent-player--theatre class being added or removed. When theatre mode is active, stats icon mounted into .player-controls__right-control-group instead, appearing on hover alongside other player controls. When exiting theatre mode it returns to its normal position.

Tested: stats icon appears correctly in theatre mode on hover, and returns to its normal position when exiting theatre mode.

Note: Pre-existing issue exists where stats icon doesn't appear on fresh page load until the setting is toggled off/on. This predates this fix.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged

Images

In Theatre Mode (visible on hover like the rest of the normal buttons)