Adds a cookbook recipe + runnable showcase that gives the Built-in Agent
OAuth-backed Arcade tools (Gmail, Google News) and renders Arcade's one-time
authorization step as a generative-UI "Connect" card in the chat.
- docs: showcase/shell-docs/src/content/docs/cookbook/arcade.mdx (+ meta.json, index card)
- app: examples/showcases/arcade-tools (Next.js App Router, single-route runtime)
Co-authored-by: Cursor <cursoragent@cursor.com>
Thierry Damiba