Records every call as an Action and lets tests program hierarchy,
screenshot, health, and per-method failures. Actions() returns a
copy so test code can't mutate the driver's history.
Accept waits for an SDK HELLO then hands back a Conn. Conn.Snapshot
sends a PAUSE, blocks on the matching STATE (id-correlated), and
leaves the SDK paused until Release sends RESUME. Conn.Close sends
GOODBYE best-effort.
v0.1 supports one client at a time; transport is left to the caller
so tests can use TCP loopback while production wires via adb reverse
to localabstract:uatu-agent.
pj