Public GitHub repos with an agent-instruction file

Built from a stratified sample of 3,478 public repos (about 500 per file pattern) that currently contain one of the seven files. For each sampled repo, the earliest commit touching that specific file gives the “first appearance” date; counts are aggregated by month and scaled to the snapshot total of 153,200 matching files. Same methodology in every month, so the line is apples-to-apples end to end.