fix: skip push when local repo has no commits (empty clone)

The smoke test clones from an empty Forgejo repo, so there are no
refs to push. Skip the push and verification gracefully when HEAD
does not resolve.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bin/disinto

@@ -674,6 +674,12 @@ push_to_forge() {
   fi
   echo "Remote:  forgejo -> ${display_url}"
 
+  # Skip push if local repo has no commits (e.g. cloned from empty Forgejo repo)
+  if ! git -C "$repo_root" rev-parse HEAD >/dev/null 2>&1; then
+    echo "Push:    skipped (local repo has no commits)"
+    return 0
+  fi
+
   # Push all branches and tags
   echo "Pushing: branches to forgejo"
   if ! git -C "$repo_root" push forgejo --all 2>&1; then