Update OpenAI SDK CSP documentation for PR #1059

[mintlify]

Updated the OpenAI SDK Architecture documentation to reflect the more permissive CSP configuration introduced in PR #1059. Both CSP modes now allow all https: sources, simplifying widget development but reducing security isolation.

Changes:

• Updated CSP header generation code example to match new implementation
• Changed CSP mode descriptions to reflect that both modes are now permissive
• Corrected file paths from server/routes/mcp/chatgpt.ts to server/routes/apps/chatgpt.ts
• Added notes about widget CSP metadata not being enforced
• Updated security best practices to acknowledge permissive CSP configuration

Files changed:

• docs/contributing/openai-sdk-architecture.mdx - Updated CSP documentation, file paths, and security notes