Add demo that runs an example agent & publishes the resulting AgentRun to a WebRegistry server running locally

[andyk]

Currently, running a example agent using the included registry file (components.yaml) creates a Run of a Component with a LocalRepo, which can't be "published" (i.e., added to a WebRegistry) because it doesn't provide reproducibility. Specifically, the WebRegistry.add_repo_spec() requires the spec that is passed in to have a url attribute.

Component.to_frozen_registry() handles this for the case of a component that has a dependency on a local repo, so we should be able to use this or extend it as necessary in a demo.