why

Explain why code exists by finding the session that produced it.

Steps

1. Call why_did_this_change with the user's target as target:

   • A file → src/cache.ts
   • A specific line → src/cache.ts:142 (pins the commit via git blame)
   • A commit → a sha, tag, or HEAD~2
   • A topic → free text (searches sessions in this repo, no git)

   The tool is read-only: it never writes to the repository.