Fix stuck station runs with a clear error

A station run could get stuck on a spinner with no explanation when the test process was blocked before it could start — often by antivirus or endpoint-protection software holding the newly launched process on a locked-down machine.

• Fixed runs hanging indefinitely: the station now surfaces a clear, actionable error instead of an endless spinner when a run cannot start.
• Added a "still starting" hint in the operator UI that points you to the terminal if a run is slow to begin.
• Improved crash messages so a failed run tells you whether it hit a Python error or was stopped from outside.