feat(models): add step 3.5 flash

[guozixu2001]

📝 Change Type

Please select the type of change this PR introduces (choose one or more):

• feat: New feature.

💡 Description

add step3.5 flash model

Key Changes

1. add step3.5 flash monkey patch

✅ Checklist

Please ensure the following points are addressed before merging:

• I have performed a self-review of my own code.
• I have added/updated tests that prove my fix or feature works (if applicable).
• I have updated the documentation (if necessary).
• My code follows the project's style guidelines.

[TianyiZhao1437]

Close for not ready. Will open later.