feat: Add anonymous analytics via GoatCounter

[pranshuparmar]

Description

This PR adds optional, privacy-respecting analytics to the playground using GoatCounter. The implementation tracks key user interactions (tutorial started/completed, tasks resolved, TUI opened, install command copied, scenario switches, and outbound clicks) while maintaining the principle that the playground never depends on analytics.

The analytics.js module is a thin wrapper that silently no-ops when the GoatCounter script is blocked by adblockers, offline, or unavailable. Events are deduplicated per page load and queued until the counter script loads, with automatic retry logic. The dashboard is public at https://witr.goatcounter.com.

A footer note discloses the analytics to visitors, emphasizing that nothing is stored in their browser.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Changes

• docs/js/analytics.js (new): Thin wrapper around GoatCounter with queue/retry logic and deduplication
• docs/js/app.js: Integrated track() calls at 8 key user interaction points
• docs/index.html: Added GoatCounter script tag and footer disclosure note
• docs/css/styles.css: Styled the stats disclosure footer
• docs/README.md: Documented the analytics implementation and privacy approach

Checklist

• I have performed a self-review of my own code
• I have added helpful comments where needed
• I have made corresponding changes to the documentation
• My changes generate no new warnings

Test Plan

The analytics module is defensive by design—all calls are silent no-ops if GoatCounter is unavailable. Manual verification:

1. Open the playground and verify the footer disclosure appears
2. Open DevTools and confirm no errors occur (analytics failures are caught)
3. Verify key interactions trigger tracking (tutorial start, task completion, TUI open, etc.)
4. Test with adblocker enabled to confirm the playground functions normally
5. Check the public dashboard at https://witr.goatcounter.com to see aggregated stats

https://claude.ai/code/session_01K4HgTJBEvAQBjstvdUcrYQ