- Change selector from [data-text], [data-kind] to .layer-spans rect, .layer-confidence-heatmap rect
- Use mouseenter/mouseleave instead of mouseover/mouseout per spec
- Handle heatmap cells (data-char) and span rects (data-text) separately
- Remove references to non-existent data attributes (bbox, blockRef, mcid, readingIdx)
- Add capture flag to event listeners for proper event delegation
This fixes the tooltip behavior to match the acceptance criteria:
- Tooltip shows text/font/confidence for spans
- Tooltip shows char/confidence for heatmap cells
- Tooltip appears on hover and disappears on leave
- Auto-repositions near viewport edges
Closes pdftract-3mdb7