Ability to decide when to forcibly stop runs

Currently, pressing the "Stop" button sends a SIGINT signal to the process, followed by a 30-second grace period. If the process hasn't stopped by then, a SIGKILL signal is sent.

This isn't ideal. Stopping and cleaning up sometimes takes longer than 30 seconds. Forcibly killing the process often leaves behind a dangling state lock, an out-of-sync state file, or a corrupted state file.

I'd like the "Stop" button to change to "Forcibly stop" after the first press, letting me decide when to force termination. If I don't press it again, the run timeout would eventually stop the process automatically.