Power Monitor now works on desktop Macs

The Power Monitor finally works on desktop Macs. On a Mac mini, Mac Studio, or Mac Pro it used to sit on "Waiting for power telemetry" forever, or show "No Power Data" on a Mac that was plainly charging things. That's fixed.

What changed

• Per-port power on desktops. Desktop Macs have no battery controller, so the readings the laptop version relies on simply aren't there. The numbers live in a different place on these machines (the SMC), and WhatCable now reads them and shows live per-port volts, amps, and watts, on the correct physical port.
• No more endless spinner. A desktop that genuinely can't report per-port power (some older models) now says so plainly instead of spinning forever.
• Laptops are unchanged.

Desktop owners: please help us check it

This is brand new and I don't have a desktop Mac to test it on. If you have a Mac mini, Studio, or Mac Pro, open the Power Monitor with something charging from a USB-C port and let me know if the numbers look right. Reports very welcome on issue #291.

Big thanks to @jimmyorz, whose Mac mini diagnostic data made this possible.