fix: app does not gracefully stop a model

[louis-jan]

Describe Your Changes

This is to reduce the duplication of nitro-killing requests. One at a time

Noticed the same while using the context length slider.
Each numerical change during a single slide triggers a nitro kill.
This spam can lead to a limbo state where nitro is not stopped and time-out messages flood the logs.

Fixes Issues

• bug: doesn't gracefully stop a model #2486

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed