Cyrus Setup Claude Auth

This handles the authentication setup for Claude Code within Cyrus, letting you choose between your current Claude CLI session, a direct API key from console.anthropic.com, a separate OAuth token, or third party providers like Bedrock and Vertex. The implementation is security focused: it never reads secrets into context and instead uses bash commands to append credentials or opens your GUI editor for manual pasting. It checks if auth already exists before running, verifies the credential was actually written, and walks you through the clipboard or terminal workflow depending on your OS. Useful for initial Cyrus setup or when switching between authentication methods without accidentally leaking tokens into the conversation history.