[Discovery] github-mcp-server - GitHub API Integration

## Project Association

This issue tracks the `github` MCP server in the core profile.

### Server Details
- **Name**: github
- **Source**: https://github.com/github/github-mcp-server
- **Docker Hub**: `ghcr.io/github/github-mcp-server`
- **Category**: git
- **Language**: Go

### Transport Status
- **Current**: stdio only (upstream)
- **Implementation**: HTTP-wrapped via supergateway
- **Docker Image**: `github-mcp:http` (custom build)

### Tools Provided
- `search_repositories`: Find repositories by name/description
- `search_code`: Search code across repositories
- `search_issues`: Search issues and PRs
- `search_users`: Find GitHub users
- `get_file_contents`: Read file/directory contents
- `create_or_update_file`: Create or update a file
- `push_files`: Push multiple files in a single commit
- `create_repository`: Create a new repository
- `fork_repository`: Fork a repository
- `create_branch`: Create a new branch
- `list_commits`: List commits in a repository
- `create_pull_request`: Create a new PR
- `list_pull_requests`: List PRs in a repository
- `merge_pull_request`: Merge a PR
- `get_pull_request_diff`: Get PR diff
- `create_issue`: Create a new issue
- `list_issues`: List issues in a repository
- `update_issue`: Update an existing issue
- `add_issue_comment`: Add comment to an issue

### Docker Status
- Official image: `ghcr.io/github/github-mcp-server`
- Custom wrapper: `github.dockerfile`
- HADOLint: Not checked

### Notes
- Official GitHub server, well-maintained
- Comprehensive GitHub API coverage
- Requires `GITHUB_PERSONAL_ACCESS_TOKEN`

### Tracking
- [ ] Document all tools comprehensively
- [ ] HADOLint compliance check
- [ ] Monitor upstream for native HTTP support