Account for EMU Accounts when creating new repository and using search

### Feature summary

For EMU accounts authenticated to the app, show only Internal/Private visibility options for repo creation, and prioritize search results to Enterprise

### What problem are you trying to solve?

When authenticated with an Enterprise Managed User account, starting a new session and choosing GitHub Respository > Create New, the options displayed to the end users for repo visibility are Public/Private. This feature request is to intelligently display only Internal/Private when authenticated with an EMU account.

Additionally, when searching by project name to start a session from an existing repo, public repos are displayed in the pick list, diluting the results. Prioritizing repos from the user's Enterprise would improve the experience.

### Proposed solution

Show only Internal/Private as repo visibility options when choosing to create a new repo from the new session flow.

Prioritize repo search results from the Enterprise the EMU user belongs to.

### Workflow impact

Enterprise Managed User organizations.

### Installation context

_No response_

### Additional context

_No response_

GitHub Repository > Create New の新しいセッションフローと、issue で言及されている既存リポジトリのプロジェクト名検索から始めます。認証済みアカウントと Enterprise コンテキストが両方のワークフローにどのように到達するかを追跡します。EMU ユーザーに表示される可視性オプションが Internal/Private のみになり、検索結果で Enterprise リポジトリが優先されれば完了です。

索引モデルが issue の本文から書いたものです。