Integrate Fusion Agent Panel

Wire a Flows/Dune app into the Fusion built-in PAIA agent using @cognite/app-sdk.

There are three independent capabilities — implement only the ones needed:

1. Open the agent panel — a button that shows the sidebar/fullscreen agent UI
2. Send the agent a message — inject context into the chat (e.g. on item click)
3. Register an agent server — expose app state (resources) and actions the agent can call

Step 0 — Understand the app

Before writing any code, read:

• package.json — detect package manager and whether @cognite/app-sdk is already installed
• src/App.tsx (or main entry) — understand current structure, existing SDK usage