Fix Julia cache flood in CI workflows

.github/workflows/cleanup-caches.yml

@@ -1,6 +1,10 @@
 name: Cleanup github runner caches on closed pull requests
 on:
-  pull_request:
+  # pull_request_target is required so fork PRs can delete their own caches on close.
+  # pull_request from a fork ships a read-only GITHUB_TOKEN regardless of the
+  # permissions: block, causing gh cache delete to fail with HTTP 403.
+  # Safe here: no PR code is checked out, the workflow only calls gh cache list/delete.
+  pull_request_target:
     types:
       - closed
 

.github/workflows/test-smokes.yml

@@ -223,7 +223,7 @@ jobs:
           version: "1.12.5"
 
       - name: Load Julia packages from cache
-        uses: julia-actions/cache@v2
+        uses: julia-actions/cache@v3
         with:
           cache-name: julia-cache;workflow=${{ github.workflow }};job=${{ github.job }};julia=${{ steps.setup-julia.outputs.julia-version }}