Introduce `McpCommand` enum and handlers in `owlen-cli` to manage MCP server registrations, including adding, listing, and removing servers across configuration scopes. Add scoped configuration support (`ScopedMcpServer`, `McpConfigScope`) and OAuth token handling in core config, alongside runtime refresh of MCP servers. Implement toast notifications in the TUI (`render_toasts`, `Toast`, `ToastLevel`) and integrate async handling for session events. Update config loading, validation, and schema versioning to accommodate new MCP scopes and resources. Add `httpmock` as a dev dependency for testing.