fix(web): preserve embedding dimensions in gateway

[marius-kilocode]

Preserve embedding dimensions in the embeddings gateway body so Codestral requests keep the hosted catalog's 256-dimensional contract.
Continue removing native Mistral-only fields while covering the Codestral proxy shape in the sanitizer tests.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

The change correctly un-strips dimensions from the upstream embedding body so the Codestral (and any other provider honouring the standard parameter) receives the vector-size contract, while continuing to strip the native Mistral-only fields (output_dtype, output_dimension) and the deprecated user field. Tests are well-targeted and cover the new behaviour.

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/embeddings/embedding-request.ts
• apps/web/src/lib/ai-gateway/embeddings/embedding-request.test.ts

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_{Reviewed by claude-sonnet-4.6 · 265,867 tokens}

_{Review guidance: REVIEW.md from base branch main}