FOLLOW-UP: Add Unicode task text test case (from PR #145)

[adnaan]

Context

This follow-up task was identified during the review of PR #145.

Source PR: #145
PR Title: feat: auto-interactive markdown checkboxes
Suggested by: @claude-bot
Priority: Low

Task Description

Add unit and/or E2E tests for task list items containing Unicode text:

• CJK characters: - [ ] 买菜
• Emoji: - [ ] 🎉 Celebrate
• RTL text: - [ ] مهمة
• Mixed scripts: - [ ] Task タスク

Verify that:

1. Detection correctly identifies these as task items
2. Slugification of Unicode headings works (or gracefully skips)
3. Rendering and persistence round-trips correctly

Original Comment

Add Unicode test case

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This issue was automatically created by prmonitor from PR review comments.