Add setting for default summarization LLM

[ifsheldon]

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• Completed

Describe the feature

When I try to configure my custom models, I found that it seems the default model used for summarizing a conversation title is the default for conversation. It will be a saving if the model for title summary can be configured to be cheaper ones. This will save a lot especially when a conversation goes long and a re-summarization is triggered manually by the user.

Environment

Zed: v0.160.7 (Zed)
OS: macOS 15.2.0
Memory: 128 GiB
Architecture: aarch64

If applicable, add mockups / screenshots to help present your vision of the feature

No response