GitHub connector: missing "Administration" permission blocks repository creation via API

### Problem Statement

The GitHub remote MCP connector (Claude Github MCP Connector app, used by claude.ai / Cowork via the GitHub-hosted official MCP server) exposes a `create_repository` tool, but it always fails with a 403 error.

Root cause: the GitHub App only requests repository-level permissions (Read: actions, metadata; Read/write: code, discussions, issues, pull requests, repository projects). It does not request the "Administration" permission on the user account, which GitHub requires for `POST /user/repos` (creating a new repository).

Repro:
1. Install/authorize the "Claude Github MCP Connector" app on a personal account via the full "Install & Authorize" flow (not just re-authorizing an existing OAuth token), with Repository access set to "All repositories".
2. Confirm in Settings → Applications → Installed GitHub Apps → Claude Github MCP Connector → Configure that only two permissions are listed: "Read access to actions and metadata" and "Read and write access to code, discussions, issues, pull requests, and repository projects".
3. Call the `create_repository` tool via the MCP connector.
4. Result: `failed to create repository: POST https://api.github.com/user/repos: 403 Resource not accessible by integration`.

All other repo-scoped write operations (push_files, create_or_update_file, issue_write, pull_request_review_write, etc.) work correctly once a repository already exists — this is specifically about creating new repositories. It also blocks creating issues/PRs on repositories the connector's installation doesn't already have access to (e.g. third-party public repos), since the installation token is scoped only to repos granted at install time.

Workaround currently in use: create the empty repository manually via the GitHub web UI (or the Claude in Chrome browser tool), then use the MCP connector's file/content tools to populate it. This works but defeats the purpose of a fully API-driven workflow.

### Proposed Solution

Add "Administration: Read and write" to the Claude Github MCP Connector app manifest so `create_repository` can succeed for accounts that have installed the app with "All repositories" access. Existing installations would surface GitHub's standard permission-update prompt, which users can review and accept individually (opt-in, same pattern as suggested in #403).

### Alternatives Considered

Creating the repository manually via github.com (or via the Claude in Chrome browser tool, driven by the same Claude session) and then using the MCP connector's API tools (push_files, create_or_update_file) to populate it. This works reliably but requires a manual browser step for every new repository.

### Area

MCP Connector (adding/managing servers)

### Priority

High - Major improvement needed

### Additional Context

Related to #403, which reports a similar "permission missing from app manifest" gap (Organization: Members) for the same connector app — same root cause pattern (installation permissions fixed by the app manifest, not user-configurable).