Add Gemini experimental model

[maelp]

I have this error

 status_code: 429, model_name: gemini-2.5-pro-preview-03-25, body: {             │
 │    "error": {                                                                    │
 │      "code": 429,                                                                │
 │      "message": "Gemini 2.5 Pro Preview doesn't have a free quota tier. Please   │
 │  use Gemini 2.5 Pro Experimental (models/gemini-2.5.pro-exp-03-25) instead. For  │
 │  more information on this error, head to:                                        │
 │  https://ai.google.dev/gemini-api/docs/rate-limits.",                            │
 │      "status": "RESOURCE_EXHAUSTED",

[geekforbrains]

I regularly get this error too as well as "INTERNAL" errors from Gemini. It seems inconsistent. The model is already added and supported in Sidekick, but we need a better way to handle these types of errors.