## ADDED Requirements

### Requirement: AgentIdPClient class exists and handles auth transparently
The SDK SHALL provide an `AgentIdPClient` class that accepts `baseUrl`, `clientId`, and `clientSecret` in its constructor and manages token acquisition and refresh automatically. Callers never handle tokens directly.

### Requirement: TokenManager caches and refreshes tokens
The SDK SHALL cache the access token in memory and re-issue it via `POST /token` when it is expired or within 60 seconds of expiry. Token refresh is transparent to the caller.
