go

The Go toolchain as a module (novox/hq ADR 0477 clause 4, issue 1573).

The only module that declares the package go. checks/toolchains refuses any other that does.
Provides go-toolchain with the machine's reach: dev-tools, lab and mesh-build-go require it, so each composes only on a machine where this module is assigned. It is never pulled in for whatever asked, so go is assigned to a node on purpose, and a node without it refuses those modules at resolution.
Holds no long-running resource, so it adds nothing to health-undeclared.

The node-engine never uninstalls a package, so moving the declaration here removed nothing from a node.