refactor: redesign media debug overlay as vertical key-value panel

[joaner]

Summary

• Refactor media debug overlay from a crowded single-line layout to a vertical key-value panel (Stats-for-nerds style)
• Remove redundant Feature / dtype / title fields that are already clear from panel context
• Enable hover-to-show with selectable values for copy, plus scroll when content is tall

Test plan

• Hover a video panel and confirm debug info appears as one property per row
• Hover an image panel and confirm the same vertical layout
• Confirm Feature / dtype / title are no longer shown
• Select and copy a value (e.g. resolution or codec) from the overlay
• Verify overlay does not cover most of the media when many fields are present