Add comprehensive tests to ensure the tooltip formatter correctly displays
actual axis values instead of numeric indices. This prevents regression of
the bug fixed in the previous commit where tooltips showed "0 (1)" instead
of actual labels like "Monday (Morning)".
Tests cover:
- Tooltip displays actual axis values with alphabetical sorting
- Tooltip works correctly with different sort orders (asc/desc)
- Tooltip works correctly with value-based sorting
- Percentage calculations use actual values when normalizeAcross is enabled
- Tooltip handles numeric axes correctly
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
