fix ROS2 Jazzy CI: force sequential executor for colcon

Jazzy CI has parallel build race condition where cloudini_ros starts
before cloudini_lib installs. Using sequential executor to fix.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: facontidavide

.github/workflows/ros-jazzy.yaml

@@ -36,3 +36,9 @@ jobs:
             cloudini_ros
           target-ros2-distro: jazzy
           skip-tests: true
+          colcon-defaults: |
+            {
+              "build": {
+                "executor": "sequential"
+              }
+            }