Unexpected revving at idle? 2019 Mazda CX-5 Purge Valve Malfunction and Replacement

Diagnosing and replacing a purge valve (aka vapor canister purge solenoid or purge valve solenoid) in a 2019 Mazda CX-5. Seems like an increasingly common problem that's hard to diagnose, even at the dealership. Some people think it's the MAF sensor, others suspect vacuum leaks, but this was the fix that worked for me. There was one other video showing the problem, but none showing the fix. Symptoms: Revving at idle, either in park, neutral, or in gear. Check engine light came on. Can be intermittent, but eventually you gotta deal with it. Another video showed code PO171 in the diagnostics. Also it would stall while starting ONLY right after filling up with gas. Part: Vapor Canister Purge Solenoid - Mazda OEM (PE01-18-751)