Gemini Code Assist Standard Too few available models

### What happened?

I am signed in to Gemini CLI with a Google account that has a Gemini Code Assist Standard license，However, there are too few available models.Where did the gemini 3.1 pro preview and gemini 3.6 flash go? /model The command displayed the model as gemini-3-pro-preview instead of gemini-3.1-pro-preview, and the latest gemini-3.6-flash model was also missing.

### What did you expect to happen?

Those holding a Gemini Code Assist Standard license should possess the latest model.

### Client information

About Gemini CLI
│
│ CLI Version 0.55.1
│ Git Commit 41327e407
│ Model Auto
│ Sandbox no sandbox
│ OS win32
│ Auth Method Signed in with Google
│ Tier Gemini Code Assist Standard

### Login information

Signed in with a Google account (OAuth). The CLI reports the tier as Gemini Code Assist Standard.

### Anything else we need to know?

_No response_

Reproduce the issue with Gemini CLI 0.55.1 on Windows using a Google account with a Gemini Code Assist Standard license, then run /model and compare the available models with the expected Gemini 3.1 Pro Preview and Gemini 3.6 Flash entries. Done means the licensed account exposes the expected latest models, or the CLI clearly identifies why they are unavailable.

Written by the indexing model from the issue text.