Add support for customizable terminal shell configuration

Add support for customizable terminal shell configuration (e.g., zsh, git bash, bash)

**Description:**

Currently, the terminal only supports the default system shell. Users should be able to configure their preferred shell environment (e.g., zsh, git bash, bash, PowerShell, etc.) in the terminal settings.

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| Field | Value |
| --- | --- |
| App version | 1.1.10 |
| OS | Windows 10.0.26200 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Day 4 (Week 1) |

首先找到终端设置 UI 以及启动系统默认 shell 的代码。跟踪 shell 选择的存储方式及其传递到终端的过程，包括列出的 zsh、Git Bash、bash 和 PowerShell 示例。完成的标准是：用户可以在终端设置中选择首选 shell，并且新的终端会话使用该选择。

由索引模型根据 Issue 内容生成。