internal/rosa: remove global handles

These no longer serve any purpose.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/stage0.go

@@ -5,6 +5,10 @@ import (
 	"hakurei.app/internal/pkg"
 )
 
+// Stage0 is the handle of the stage0 distribution tarball built on the
+// toolchain of stage [Std].
+var Stage0 = H("rosa-stage0")
+
 func init() {
 	meta := Metadata{
 		Name:        "rosa-stage0",
@@ -13,7 +17,7 @@ func init() {
 	}
 	native.MustRegister(meta.Name, func(t Toolchain) (*Metadata, pkg.Artifact) {
 		return &meta, t.New("rosa-stage0", 0, t.Append(nil,
-			Bzip2,
+			H("bzip2"),
 		), nil, nil, `
 umask 377
 tar \