This PR changes all `lean-toolchain` to use relative toolchain paths
instead of `lean4` and `lean4-stage0` identifiers, which removes the
need for manually linking toolchains via Elan.
After this PR, at least Elan 4.2.0 and 0.0.224 of the Lean VS Code
extension will be needed to edit core.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
This PR adds some information to Grove: a check that all
string/slice-transforming functions are tracked properly (which finds
dozens of missed cases), and some documentation of design designs around
naming in the string library.
The PR also bumps the Grove version to the latest version which contains
many new features and also processes the data a lot faster (40s to 2.5s
for the test project).
