fix(ui): render html tables

[ChEnylnti]

Summary

Render HTML tables in problem descriptions instead of flattening their cells into plain text.

This adds a table tag renderer that:

• preserves rows and columns from <table>, <tr>, <th>, and <td>
• supports tables nested inside block containers like <div class="example-block">
• wraps long cell content based on the description window width
• draws row separators to keep table structure readable in terminal UI

Verification

• Verified a minimal top-level table renders correctly
• Verified a table nested inside <div> renders correctly
• Verified the real LeetCode CN problem best-time-to-buy-and-sell-stock-using-strategy renders its example tables with rows, columns, and separators