Change in handling of IdentityAgent on Windows OpenSSH 8.9

[3b0b]

Submitting this here in case it helps anyone else. The short version is:

IdentityAgent \\.\pipe\krd-agent

in my ssh config stopped working; either removing that line and setting $env:SSH_AUTH_SOCK or changing it to

IdentityAgent //./pipe/krd-agent

fixed it for me. See https://github.com/PowerShell/Win32-OpenSSH/issues/1949.