claude_agent_sdk's _AsyncioTaskHandle.wait() uses
`with suppress(asyncio.CancelledError)` to silence the inner read
task's expected cancellation, but it also swallows the outer task's
cancellation if it lands on the same await — causing cancel_task to
time out.
Bypass `async with ClaudeSDKClient` and drive connect/disconnect
ourselves so disconnect() runs in a finally where the outer
CancelledError has already been raised and suspended by Python's
exception machinery, out of reach of the SDK's suppress.