CHECKSUMS.txt lists a SHA-256 for every top-level .ps1 and .cmd - the files a
user actually executes. zchecksums verifies them; zchecksums -Update
regenerates after an intentional edit.
The manifest is sha256sum format, so 'sha256sum -c CHECKSUMS.txt' works on
Linux/macOS/WSL as well as the PowerShell path on Windows. Hashes are identical
on every platform because .gitattributes pins .ps1/.cmd to CRLF everywhere -
that pin is now load-bearing, so it is commented as such.
Beyond changed and missing files it also reports a script that is on disk but
NOT in the manifest, so something added outside a commit still gets noticed.
Exits non-zero on any of the three.
Honest about its limits, in the header and the README: the manifest lives in
the same repo as the code, so it is an integrity check rather than a signature.
It catches a truncated clone, a forgotten local edit, or an unlisted file - not
a compromised repo.
CHECKSUMS.txt is pinned to LF: sha256sum treats a trailing CR as part of the
filename and would report every entry as missing on Linux.
tests/Checksums.Tests.ps1 keeps it from rotting - a stale manifest is worse
than none, since it either cries wolf until people ignore it or quietly stops
covering a new script. The tests assert the format, LF endings, sort order,
full coverage of on-disk scripts, current hashes, and that zchecksums itself
exits 1 on a tampered file (proved by appending a byte and restoring it).
