fix: use SIGKILL and StopCommand in lifecycle example

[joshrotenberg]

Summary

Fixes the lifecycle_commands example which was failing on Windows (and potentially other systems) because:

1. KillCommand with SIGTERM doesn't guarantee immediate container termination
2. The 1 second sleep wasn't enough for the container to fully stop
3. RmCommand without --force fails on running containers

Changes

• Use SIGKILL instead of SIGTERM for the kill demo (immediate termination)
• Added a second section demonstrating the proper stop -> rm pattern
• Print the stopped container names from StopResult instead of discarding the result

Testing

Verified the example runs successfully:

cargo run --example lifecycle_commands

Fixes #201