## Why
The SIGTERM cleanup test depends on the OS scheduling the shell within the production grace period. Tracing tests also need fixture creation and cleanup to use the appropriate subscriber.
## What changed
- Pause Tokio time while waiting for the shell's cleanup marker, keeping the cancellation future runnable to prevent automatic clock advancement, then resume time after execution.
- Adjust subscriber setup and fixture lifetimes in session and tool dispatch tests so instrumented resources are created and dropped under the appropriate subscriber.
GitOrigin-RevId: 12c654a031a8a4e61fc66488a5f687852f5ca099