Pls give us option to disable worktrees globally in settings.

### Feature summary

_No response_

### What problem are you trying to solve?

When I start a new session in a folder that has 40 repos (welcome to my world), It's really annoying to have to specify 40 branches, and toggle 40 worktree toggle's off. And even when they are off, it still creates worktrees.

### Proposed solution

Global setting to turn off all worktree related stuff. (this toggle should also leave the branches as they were)

### Workflow impact

This would massively help people who don't need worktrees.

### Installation context

_No response_

### Additional context

GitHub CoPilot Desktop app v1.0.25

首先定位应用设置，以及会在多个仓库之间创建 worktree 的会话设置路径。确认每个仓库的 worktree 开关和分支选择是如何应用的。当全局设置禁用 worktree 创建，并使所有仓库中的现有分支保持不变时，即视为完成。

由索引模型根据 Issue 内容生成。