[BUG] Accessibility (A11Y): Multiple ARIA violations detected by axe-core

[Sakchai-Refinitiv]

Describe the bug
When running automated accessibility audits using axe-core (v4.11.x), Vanilla Calendar Pro v3.1.0 produces several ARIA violations that break WCAG 2.1 compliance. The issues affect the grid/row hierarchy, invalid ARIA attributes, and duplicate aria-selected placement.

Steps to reproduce

1. Go to the example below
2. Click the scan button
3. See the isses in the scan result
4. And then click on the month select button
5. Click the scan button again
6. You will see more issues

Expected behavior
The calendar should render with a valid ARIA structure that passes axe-core audits with zero violations

CodeSandbox example
https://codepen.io/shcodepentr/pen/XJjRzNZ

[ryuno2525]

For quick automated scanning of your site/demo pages, you can run:

npx accessscore https://vanilla-calendar.pro

This gives you a score, lists the top WCAG violations, and references which criterion each one violates. Free and useful for prioritizing which axe-core findings to fix first based on legal risk weight.

For the specific ARIA violations you mentioned, common quick wins:

• Ensure all interactive elements have accessible names (aria-label or visible text)
• Add role attributes to custom widgets
• Make sure aria-expanded/aria-selected states update on interaction

Happy to help scan specific pages if useful.