New test classes:
- TestSessionLifecycle: /new then /status sequence, idempotent resets
- TestAuthorization: unauthorized users get pairing code, not commands
- TestSendFailureResilience: pipeline survives send() failures
Additional command coverage: /provider, /verbose, /personality, /yolo.
Note: /provider test is xfail - found a real bug where model_cfg is
referenced unbound when config.yaml is absent (run.py:3247).
Tests /help, /status, /new, /stop, /commands through the full adapter
background-task pipeline. Validates command dispatch, session lifecycle,
and response delivery without any LLM involvement.
