fix: run required labels on pull_request_target

Author: Kaiser-Wu

.github/workflows/required-labels.yml

@@ -1,6 +1,8 @@
 name: Required Labels
 on:
-  pull_request:
+  # Run on the base repository context so fork PRs can still post label reminders.
+  # This workflow does not check out or execute PR code; it only inspects PR metadata.
+  pull_request_target:
     types: [opened, labeled, unlabeled, synchronize]
 jobs:
   label:
@@ -22,4 +24,4 @@ jobs:
             chore
             documentation
           add_comment: true
-          message: "Requires label: feature, enhancement, fix, bugfix, bug, chore, documentation."
+          message: "Requires label: feature, enhancement, fix, bugfix, bug, chore, documentation."