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_

Start with the new session flow at GitHub Repository > Create New and the existing-repository project-name search mentioned in the issue. Trace how the authenticated account and Enterprise context reach both workflows. Done means EMU users see only Internal/Private visibility options and enterprise repositories are prioritized in search results.

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