fix(ci): run Windows free tests on every push to main (GSTA-68 follow-up)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

.github/workflows/windows-free-tests.yml

@@ -23,6 +23,11 @@ name: Windows Free Tests
 on:
   pull_request:
     branches: [main]
+  # Also on main pushes, as free-tests.yml does: trains dispatch only the
+  # Linux free workflow, so without this no Windows run ever sees a train's
+  # combined tree or main after a merge.
+  push:
+    branches: [main]
   workflow_dispatch:
     inputs:
       record_durations: