pricing-update(vertex-ai): add Grok 4.3 model config and pricing

[akhilmmenon]

Summary

• Adds grok-4.3 to the Vertex AI general schema with support for image input and function calling
• Adds tiered pricing for grok-4.3 on Vertex AI with context-length-based pricing (≤200k and >200k input tokens)

Pricing details

Tier	Input / 1M tokens	Output / 1M tokens	Cached Input / 1M tokens
≤ 200k prompt tokens	$1.25	$2.50	$0.20
> 200k prompt tokens	$2.50	$5.00	$0.40

References

• Vertex AI Grok 4.3 model card
• xAI Grok Vertex AI pricing

Test plan

• Verify pricing shows correctly in the model catalog for Vertex AI / Grok 4.3
• Verify cost attribution works for requests under and over 200k input tokens

[Copilot]

Pull request overview

This PR extends the Vertex AI model catalog by adding the grok-4.3 model to the general schema and introducing tiered (context-length-based) pricing for it in the Vertex AI pricing catalog.

Changes:

• Add grok-4.3 to general/vertex-ai.json as a chat model supporting image input and tool/function calling.
• Add grok-4.3 to pricing/vertex-ai.json with two context tiers (≤200k and >200k) and corresponding per-token and cached-input rates.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
general/vertex-ai.json	Registers grok-4.3 in the Vertex AI general model schema with supported capabilities.
pricing/vertex-ai.json	Adds grok-4.3 pricing, including context-tiered rates and cached-input pricing.

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