Flag to automatically clean up

**Describe the problem/challenge you have**
It would be nice to have a flag like `--rm` which you can pass to `start` to automatically clean up when you Cntrl+C.

**Describe the solution you'd like**
A `--rm` (or similar) flag for `start` to cleanup the secrets and pod when kwt is interrupted

Start at the `start` command and trace how interruption is currently handled. Define the `--rm` behavior so that interrupting kwt removes the associated secrets and pod, then verify cleanup through the existing command checks or tests.

Written by the indexing model from the issue text.