The stop button provides poor user feedback during the pipeline shutdown process. Currently, clicking stop leaves users waiting 5+ seconds with no indication that their action was registered or that the pipeline is terminating.

Details

• Current behavior: Stop button remains unchanged for 5+ seconds after click, then switches directly to "Run" state
• Expected behavior: Button should immediately show "Stopping..." state on click, then transition to "Run" (green) once pipeline fully terminates
• Impact: Users often click stop multiple times thinking their first click didn't register
• Component: Pipeline Observability screen stop/run controls

Acceptance Criteria

• Stop button immediately changes to "Stopping..." state when clicked
• Button is disabled during stopping state to prevent multiple clicks
• Button transitions to "Run" (green) state only after pipeline WebSocket connections on port 5565 are fully closed
• Visual styling clearly differentiates between Stop, Stopping, and Run states