[2025-11 LWG Motion 12] P3612R1 Harmonize proxy-reference operations (LWG 3638 and 4187)

[jensmaurer]

https://wiki.edg.com/pub/Wg21kona2025/StrawPolls/P3612R1.html

[AlisdairM]

If no-one else takes this, I will grab it.