[BUG] Cannot let Gemini 2.5 Pro/Flash reasoning

[Creling]

Describe the bug

When interacting with the Gemini 2.5 Pro/Flash, the reasoning feature does not seem to be activating, even though it is enabled in my model settings. Copy Response as Markdown does not contain COT content as well, when Copy including COT details is enable.

Screenshots

DeepChat Version: v0.2.6

Additional context
Add any other context about the problem here.

[zerob13]

fixed in #639