feat(provider/cartesia): add Ink 2 streaming transcription

[31Carlton7]

Summary

• add TranscriptionModelV4.doStream support for Cartesia Ink 2 using the shared WebSocket transport
• support Cartesia's native turn-detection endpoint and manual finalization while preserving the existing experimental_realtime API
• add Node/Edge coverage, provider documentation, an example, and a patch changeset

This is the streaming-transcription follow-up to #16815 and builds on the shared transport/API work from #17093, #17094, and #17095.

Testing

• pnpm --filter @ai-sdk/cartesia test
• pnpm --filter @ai-sdk/cartesia type-check
• pnpm --filter @example/ai-functions type-check
• pnpm turbo build --filter=@ai-sdk/cartesia
• pnpm validate:docs
• pnpm konsistent
• pnpm exec ultracite check <changed TypeScript files>

[github-actions]

🚀 Published in:

Package	Version
@ai-sdk/alibaba	2.0.13 github npm
@ai-sdk/amazon-bedrock	5.0.23 github npm
@ai-sdk/azure	4.0.16 github npm
@ai-sdk/baseten	2.0.11 github npm
@ai-sdk/cartesia	3.0.4 github npm
@ai-sdk/cerebras	3.0.11 github npm
@ai-sdk/deepinfra	3.0.11 github npm
@ai-sdk/fireworks	3.0.12 github npm
@ai-sdk/google	4.0.17 github npm
@ai-sdk/google-vertex	5.0.21 github npm
@ai-sdk/huggingface	2.0.11 github npm
@ai-sdk/mcp	2.0.14 github npm
@ai-sdk/mistral	4.0.12 github npm
@ai-sdk/moonshotai	3.0.13 github npm
@ai-sdk/openai	4.0.15 github npm
@ai-sdk/openai-compatible	3.0.11 github npm
@ai-sdk/react	4.0.31 github npm
@ai-sdk/togetherai	3.0.12 github npm
@ai-sdk/tui	1.0.29 github npm
@ai-sdk/vercel	3.0.11 github npm
@ai-sdk/xai	4.0.14 github npm