[no-ci] CI: test restricted-paths-review-gate via pull_request

Temporarily switch the new workflow to pull_request so PR #1896 can exercise the label-driven pass/fail behavior before the workflow exists on the base branch. This lets us validate the gate logic pre-merge and then switch back to pull_request_target for the final rollout.

Test plan:
1. Temporarily switch the new workflow to `pull_request`.
2. Push to PR `#1896`.
3. Add the label and confirm the check goes red.
4. Remove the label and confirm the check goes green.
5. Switch it back to `pull_request_target` before merging.

Made-with: Cursor

Author: rwgk

.github/workflows/restricted-paths-review-gate.yml

@@ -4,9 +4,9 @@
 name: "CI: Restricted Paths Review Gate"
 
 on:
-  # Keep this separate from pr-metadata-check.yml so only the
-  # Needs-Restricted-Paths-Review policy becomes merge-blocking.
-  pull_request_target:
+  # Temporary for PR-level testing before this workflow exists on the base
+  # branch. Switch back to pull_request_target before merging.
+  pull_request:
     types:
       - opened
       - synchronize