PR #122: Add in-process mutation testing infrastructure

Agent Instructions

Click a suite to see its builds. Example suite for 2858adeb :

https://staging.nix-ci.com/gh:NorfairKing:sydtest/refs%2Fpull%2F122%2Fmerge/2858adebfb23a8166f00efc5cefe69cafff699f6

For more instructions, fetch https://staging.nix-ci.com/instructions .