EMU migration issues in GitHub Copilot App

I have an organisation that migrated from non-EMU to EMU users.

The transition/migration from a GitHub Copilot App is quite bumpy:

- The old non-EMU user (which had the Copilot license) had to be complete remoted, so GitHub Copilot App would correctly log into the EMU organisation. The solution was to remove the non-EMU account, and the unsuccessful EMU account, and with no accounts, log in. An EMU Login with no accounts logged me in correctly into Copilot App.
- This has a side effect: The projects that were previously linked to the non-EMU account now displays the message "This project's account was Removed. Operations will use the default account. Reassign in project settings."

The only practical solution during an EMU migration is to delete all the sessions and projects, and resume. But there should a cleaner/smoother EMU migration for GitHub Clients in the App.

---
| Field | Value |
| --- | --- |
| App version | 1.1.6 |
| OS | macOS 26.5.2 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 14 |

No source files, tests, or entry points are identified. Start by reproducing the non-EMU-to-EMU migration in the GitHub Copilot App on macOS, including the removed-account project state; done requires a defined migration flow that preserves or cleanly reassigns existing projects without deleting sessions and projects.

索引モデルが issue の本文から書いたものです。