VK Cleanup 5/7: Core API reference

[siddharthsambharia-portkey]

Virtual Keys -> Model Catalog Cleanup

What's changing

Core API reference updated to promote AI Provider slug pattern. Legacy virtual_key / x-portkey-virtual-key parameters are preserved in tables marked as (Legacy) for backward compatibility.

Files changed (5)

• headers.mdx -- AI Provider section promoted; all code examples updated; legacy rows preserved with deprecation note
• gateway-for-other-apis.mdx -- Accordion renamed to Add an AI Provider; code updated
• authentication.mdx -- Code examples updated to provider="@openai-prod"
• sdk/python.mdx -- Placeholder and parameter docs updated
• sdk/c-sharp.mdx -- Prose references updated

Review checklist

• Legacy virtualKey / x-portkey-virtual-key remain in tables with deprecation note
• All code examples use provider="@openai-prod" or x-portkey-provider: @openai-prod
• Python, JS, and cURL examples are consistent

Risk: Medium

High-traffic API reference pages -- legacy backward compat preserved.