Pull 'main' from the remote when starting a new session

Pull 'main' from the remote when starting a new session

When starting a new session against an existing project that is associated with a GitHub repository, I have not found a good series of steps for ensuring the local clone has the latest 'main' branch pulled before starting that session.

Some cases where this is important:
- After a new `agent` has been added to the repo and wanting to choose that agent for the session.
- After a new `skill` has been added to the repo, and waiting to use that skill in the prompt
- After code changes have been merged into main and wanting to be sure the new worktree created for the session is based on those changes

What gesture is supposed to be used to update a project's main branch before starting a new session?

---
| Field | Value |
| --- | --- |
| App version | 1.1.12 |
| OS | Windows 10.0.26200 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 6 |

首先跟踪与 GitHub 关联的项目现有的新会话流程，以及创建 worktree 前使用的控件。确认所选手势会在会话设置之前从远程更新本地 main 分支，其中包括新添加的 agents、skills 和已合并的代码。

由索引模型根据 Issue 内容生成。