feat: add WebMCP schedule tools

[condyl]

Summary

• expose timetable creation, editing, ranking, preview, pinning, and export as browser-native WebMCP tools
• keep tool option counts aligned with the visible calendar and preserve calendar navigation after agent selection
• add read-only course-addition previews, WebMCP headers, distinct batch course colours, and regression coverage

Validation

• npm test -- --run (34 passed)
• npm run lint
• npm run build
• live WebMCP/browser audit against the calendar