build: make executable and test roots package actions

test/misc/packedwwi_test.ww

@@ -14,9 +14,9 @@ package packedwwi_test;
 // type.ha:122-126). Both driver stages must build the -I tree and run
 // exit 91 (9*10+1; a dropped @packed gives 168). Strengthened over
 // the carrier: the re-emitted `struct @packed {` is also asserted in
-// the retained sepwork pk2.wwi. A single-file two-package form
-// produces NO .wwi (one __root unit), so the real -I tree is
-// irreducible here.
+// the retained sepwork pk2.wwi. A single-file two-package form produces
+// only one raw `__root.wwi`, not an independently importable pk2 package,
+// so the real directory-package -I tree is irreducible here.
 //
 // identityreject: assigning packed A to a structurally-identical
 // unpacked B — packed is type identity (harec types.c:621). STAGE-