ci: bump dorny/paths-filter to v4 for the node24 runtime

v4.0.0 is exactly the node24 update (dorny/paths-filter#294), so the
FORCE_JAVASCRIPT_ACTIONS_TO_NODE24 workaround and its deprecation
warning both go away.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: vinidlidoo

.github/workflows/ci.yml

@@ -41,10 +41,6 @@ jobs:
   # freshness gate this very cycle).
   changes:
     runs-on: ubuntu-latest
-    # paths-filter@v3 still ships on Node 20 (deprecated June 2026); opt it into
-    # Node 24 now so it doesn't break when the runner drops Node 20.
-    env:
-      FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: 'true'
     outputs:
       viewer: ${{ steps.filter.outputs.viewer }}
       agent: ${{ steps.filter.outputs.agent }}
@@ -57,7 +53,7 @@ jobs:
       # the GitHub API and works without checkout — which is why this job passed
       # on the PR but failed exit-128 on push-to-main without this step).
       - uses: actions/checkout@v5
-      - uses: dorny/paths-filter@v3
+      - uses: dorny/paths-filter@v4
         id: filter
         with:
           filters: |