The portable Windows job (P11c run 6) failed ledger-core's `where_backups_go_is_checked`: `/srv/books.git` is not an absolute path to Windows, and `C:\books` was read as the host `C` of a networked address. `backup.git_remote` now reads a drive path (one letter, a colon, a slash or backslash) as a path on this computer, as git does, and a path from `/` as rooted on every system git runs on; the test holds the three forms on every OS. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp