ci: Integration test against nightly docker image

Author: nealrichardson

.github/workflows/integration-tests.yaml

@@ -15,6 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         version:
+          - "preview"   # Nightly builds of Connect
           - "release"   # special value that always points to the latest Connect release
           - "2025.09.0" # jammy
           - "2025.03.0" # jammy
@@ -47,7 +48,7 @@ jobs:
         shell: Rscript {0}
 
       - name: Run integration tests
-        uses: posit-dev/with-connect@main
+        uses: posit-dev/with-connect@preview
         env:
           CONNECTAPI_INTEGRATED: "true"
         with: