docs: add TokenLab community provider

[hedging8563]

Summary

• add TokenLab to the Community Providers documentation
• document the published @tokenlabai/ai-sdk-provider package
• include model discovery, basic generateText/streamText examples, and native endpoint pointers

Verification

• git diff --check

[hedging8563]

Verification note: this is a docs-only community provider addition. I ran git diff --check locally. The Vercel status currently points to a Vercel GitHub authorization URL for the fork preview, while Socket Security and Vercel Agent Review are passing.