fix(32-06): the additive stage compares with the previous release once HEAD is tagged

- last_tag skips tags that contain HEAD, so a post-release run compares
  v0.5.1 with v0.5.0 instead of with itself

scripts/check-phase32.sh

@@ -994,9 +994,11 @@ consumer_run() {
 	return "$rc"
 }
 
-# last_tag prints the newest release tag of this checkout.
+# last_tag prints the newest release tag that does not contain HEAD: the
+# previous release, also once HEAD itself carries the new release tag (a
+# post-release run must not compare the release with itself).
 last_tag() {
-	git -C "$ROOT" tag --sort=-v:refname | head -n 1
+	git -C "$ROOT" tag --sort=-v:refname --no-contains HEAD | head -n 1
 }
 
 # base_worktree creates the last tag's worktree once (BASE_TREE).