0002: Run the mock agent on a virtual clock

Status: Accepted

Context

The runner, the VAD, and the metrics need end-to-end tests. Tests against a wall clock are slow, because a conversation takes tens of seconds, and flaky, because CI machines stall. Users also need a demo that works offline without a real agent.

Decision

The runner takes a Clock. Network adapters use RealClock. The in-process mock adapter uses VirtualClock, which advances time only when the runner sleeps, so a session runs as fast as the CPU allows and gives the same result every time.

Consequences

• The full pipeline runs in milliseconds, so the test suite, the README check, and the benchmark gate cover it on every push.
• The demo output in the README is byte-for-byte reproducible, and a test compares it with a real run.
• Real-clock behavior still needs coverage. The realtime tests run the mock agent over a local WebSocket on the wall clock.