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 |

Start by tracing the existing new-session flow for projects linked to GitHub and the controls used before a worktree is created. Verify that the chosen gesture updates the local main branch from the remote before session setup, including newly added agents, skills, and merged code.

索引モデルが issue の本文から書いたものです。