After almost two weeks of avoiding manuals, while scanning blog posts and speed-watching the occasional tutorial, the speaker attached to the DF Player Mini attached to the ESP32 board burst into song! Along the way, I procured more bread boards because the ESP32 is too big to fit on a single one and allow connections on both sides.
Of course, I spent one of those weeks trying to figure out how a months-younger version of me had successfully flashed the board. I followed a remarkably similar path to the first time, including the accidental over-writing of the boot loader, and rediscovery that PlatformIO will recover it if you can successfully talk to the device. I updated the original post with additional notes this time. Hopefully I won’t have to learn it again!
Now the circuit lacks only a limit switch and the valve switch to make the hardware complete. It’s just programming from there.
Pembroke:87 
I’m kinda at this stage with several Arduino projects. I know I had them working on the breadboard, pushed the code out to a mini and that was 6-8 months ago. Now I need to get it all checked out before hooking it up to the layout. Thanks for the inspiration to just get off my butt and do it!
How do the months slip away so quickly? Hope to hear how it went.