Make build-approved release pending PR workflows

.github/VOUCHED.td

@@ -4,7 +4,10 @@
 # its author is trusted: repository collaborators are trusted automatically
 # and do not need listing; external contributors listed here are trusted
 # too. Anyone else gets the plan only, until a maintainer either adds them
-# here or applies the "build-approved" label to that one PR.
+# here or applies the "build-approved" label to that one PR. The label also
+# releases GitHub's approval hold for that PR's build and test workflows.
+# It remains effective while attached, without vouching for the author's
+# other PRs. An explicit denouncement cannot be overridden by the label.
 #
 # Syntax:
 #   github:username