fix: Update gemini model names.

[Oht8wooWi8yait9n]

Description

This PR adds support for the new Gemini 2.5 Pro, Gemini 2.5 Flash, and Gemini 2.5 Flash Lite models in Onyx. This includes adding the model names to the backend list of available models and updating the frontend to display these models with user-friendly names. The older "preview" model names have been commented out, but retained in the code for possible future use.

How Has This Been Tested?

I verified that each new model name ("gemini-2.5-pro", "gemini-2.5-flash", and "gemini-2.5-flash-lite") works correctly when used in a search query within the Onyx application. This confirms that the models are properly integrated into both the backend and frontend and can be selected and used by users.

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Summary by cubic

Add support for Gemini 2.5 Pro, Flash, and Flash Lite by updating the backend model list and UI display names. Replaces preview IDs with stable ones; preview entries are commented out for reference.

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[greptile-apps]

Greptile Summary

This PR updates Onyx's support for Google's Gemini 2.5 models by transitioning from preview versions to stable production releases. The changes span both backend and frontend components:

Backend changes (backend/onyx/llm/llm_provider_options.py):

• Updates the VERTEXAI_MODEL_NAMES list to include three new stable model names: gemini-2.5-pro, gemini-2.5-flash, and gemini-2.5-flash-lite
• Comments out the older preview models (gemini-2.5-pro-preview-06-05 and gemini-2.5-pro-preview-05-06) rather than removing them entirely

Frontend changes (web/src/lib/hooks.ts):

• Adds display names for the new stable models in the MODEL_DISPLAY_NAMES object with user-friendly labels like "Gemini 2.5 Pro", "Gemini 2.5 Flash", and "Gemini 2.5 Flash Lite"
• Comments out display names for preview models (gemini-2.5-pro-preview-05-06 and gemini-2.5-flash-preview-05-20)

This change aligns with Google's model release cycle, where preview models are being superseded by stable production versions. The approach maintains backward compatibility by preserving commented code while providing users access to the latest stable Gemini models through the Onyx interface. The frontend display names follow existing naming conventions and provide clear, user-friendly labels for model selection.

Confidence score: 5/5

• This PR is safe to merge with minimal risk as it only updates model configuration lists
• Score reflects simple, well-tested changes that follow established patterns in the codebase
• No files require special attention as both changes are straightforward configuration updates

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[cubic-dev-ai]

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