Here's an update to the quoted content above.
An iOS application called Airfoil does, indeed, allow streaming of any audio source from Macs to Chromecast Audio devices. I purchased and downloaded the $29 app today and it works great for streaming music wirelessly from Tidal on my MacBook Pro and casting it to my music system via CCA. I simply need to identify the specific source (Tidal, YouTube, Pandora, Spotify, or web browser, etc.) via the Airfoil iOS interface and the software enables the Mac-to-CCA connection.
As I mentioned, it's a great solution for music or other audio-only streaming. However, I'm experiencing a definite lag (of 1-2 seconds) in audio+video streams (audio lags behind video). Not sure if this is an issue of my WiFi signal, or something else holding things up on the Mac, but it's unfortunate. Regardless, it's good to have the music-streaming fix in place.