Cleanup session files on get message or session deleted error

[nikola-jokic]

No description provided.

[Copilot]

Pull request overview

This PR ensures the listener cleans up local runner configuration when the server indicates the runner registration no longer exists—either during session creation (registration deleted) or while retrieving messages (not found).

Changes:

• Add a new CreateSessionResult.RunnerRegistrationDeleted outcome and return it from MessageListener/BrokerMessageListener when the service reports invalid_client.
• Handle RunnerRegistrationDeleted in Runner.RunAsync by deleting local runner config and exiting with a terminated error code.
• Catch TaskAgentNotFoundException/RunnerNotFoundException during message retrieval to delete local runner config and exit the run loop cleanly; add L0 coverage for the new behaviors.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/Test/L0/Listener/RunnerL0.cs	Adds L0 tests covering config cleanup (or non-cleanup) for session conflict, registration-deleted during session creation, and not-found during message retrieval.
src/Runner.Listener/Runner.cs	Adds handling to delete local runner config on registration-deleted and on not-found exceptions while polling messages.
src/Runner.Listener/MessageListener.cs	Extends CreateSessionResult and returns RunnerRegistrationDeleted when session creation fails due to deleted registration (invalid_client).
src/Runner.Listener/BrokerMessageListener.cs	Mirrors RunnerRegistrationDeleted handling for the broker listener’s session creation path.