Fix markdown-unsafe fallback in TurnCard.tsx

[manavgup]

Problem

There's a known TODO in the codebase that needs to be addressed:

Location: apps/web/src/components/ask/TurnCard.tsx:255

Issue: Markdown-unsafe fallback paths when slicing content

Context

The current implementation has unsafe markdown handling in fallback code paths that could lead to rendering issues or XSS vulnerabilities.

Action Required

• Review the markdown slicing logic in TurnCard component
• Implement safe markdown handling for all code paths
• Add tests to verify markdown safety
• Remove the TODO comment once fixed

Acceptance Criteria

• Markdown slicing is safe in all code paths
• No XSS vulnerabilities
• Tests added to verify safety
• TODO comment removed