feat(xai): update model YAMLs [bot]

[hganwani-droid]

Auto-generated by poc-agent for provider xai.

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Note

Medium Risk
Changes model capability/limit metadata and request-parameter filtering for XAI models, which can affect downstream request construction and validation. Risk is moderate because it may change which inputs/params are accepted at runtime.

Overview
Updates XAI model YAML metadata.

grok-2-image now declares text+image inputs and adds removeParams to strip chat-style generation parameters (e.g., max_tokens, temperature, top_p, stop, stream, n) for image requests.

grok-3-fast-latest adds the structured_output feature and expands limits by explicitly setting context_window and max_tokens to 131072.

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