CI: run the full suite on pushes to kernel-smlib

PRs into kernel-smlib only run their changed packages and the branch has no
merge queue, so nothing tested the branch as a whole. A push run after each
merge does. Caches stay main-only (save-if and the sticky-disk commit key on
refs/heads/main).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -49,7 +49,7 @@ on:
   # The merge queue: each queued group runs the full suite before it lands on main.
   merge_group:
   push:
-    branches: [main]
+    branches: [main, kernel-smlib]  # kernel-smlib: full suite after each merge into the kernel branch
   schedule:
     - cron: "17 6 * * *"
   workflow_dispatch: