Centralize Go validation and build environments

check.go

@@ -34,7 +34,8 @@ type ReleaseRequest struct {
 
 // Check validates one local, committed release candidate. It requires a clean
 // worktree and index on main, a committed note matching Product and Version,
-// and an unused local tag. If Validate is nil, the offline Go test suite runs.
+// and an unused local tag. If Validate is nil, the offline Go test suite runs
+// with the available compatible local Go toolchain and the Go host target.
 // If Build selects targets, Check builds them after validation in temporary
 // storage outside the worktree, then rechecks branch, HEAD, worktree, index,
 // and local tag state. Success establishes local candidate evidence only; it