lock dependencies

the issue

in both the base repo and the mirror, for all branches:

 error: rustc 1.78.0 is not supported by the following packages:
  rayon@1.11.0 requires rustc 1.80
  rayon-core@1.13.0 requires rustc 1.80
  rayon-core@1.13.0 requires rustc 1.80
  rayon-core@1.13.0 requires rustc 1.80
Either upgrade rustc or select compatible dependency versions with
`cargo update <name>@<current-ver> --precise <compatible-ver>`
where `<compatible-ver>` is the latest version supporting rustc 1.78.0

the fix

as pinning rayon@1.10.0 (the version in my local Cargo.lock) in Cargo.toml does not work, i had to start tracking Cargo.lock.

this adds a script to check that the lock file has not been modified after running the full CI suite.