fix: render user chat input as plain text

[mturac]

Summary

• Render user chat question content as plain text instead of passing it through the markdown renderer.
• Preserve line breaks and word wrapping in the question bubble.
• Add a regression test that verifies user-supplied HTML stays textual and does not create DOM controls.

Closes #37414

Tests

• pnpm test app/components/base/chat/chat/tests/question.spec.tsx
• pnpm eslint app/components/base/chat/chat/question.tsx app/components/base/chat/chat/tests/question.spec.tsx --fix
• pnpm type-check
• git diff --check