Update SDK quickstart snippets to use Files component

[devin-ai-integration]

Summary

Replaces bash code block file structures with the interactive <Files> component in two SDK quickstart snippets:

• option-1-openapi.mdx - OpenAPI initialization folder structure
• option-2-fern-def.mdx - Fern Definition initialization folder structure

These snippets are included in the SDK quickstart page (fern-folder.mdx), so this change improves the visual presentation of folder structures with expandable/collapsible folders and proper file icons.

Review & Testing Checklist for Human

• Verify the <Files> component renders correctly on the preview deployment - check both the OpenAPI and Fern Definition accordion sections on the SDK quickstart page
• Confirm the folder hierarchy and comments display as expected (comments should appear next to files/folders)
• Note: There's a quote character change in option-2-fern-def.mdx (' → ') - verify this doesn't cause rendering issues

Notes

• Link to Devin run: https://app.devin.ai/sessions/8ffa37cca56144f28b33cdd6512a5e82
• Requested by: unknown ()

[devin-ai-integration]

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