fix: add protected labels for internal and external contributions (#1830)

Author: mdrxy

.github/labeler.yml

@@ -100,3 +100,15 @@ tests:
       - '**/*test*.py'
       - '**/*test*.js'
       - '**/*test*.ts'
+
+# Protected labels - managed by tag-external-contributions.yml
+# These rules never match, preventing sync-labels from removing them
+internal:
+  - changed-files:
+    - any-glob-to-any-file:
+      - '.github/labeler-protected-internal-never-matches'
+
+external:
+  - changed-files:
+    - any-glob-to-any-file:
+      - '.github/labeler-protected-external-never-matches'