Remove shell VM launchers in favor of the Python ones

Delete run-*.sh and point the documentation at run-*.py. The
seediso build-seed.sh helpers stay, as the Python launchers call them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HL6bzSwWGNwru9bDS9ZCLg

run-debian13.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-"""Start the Debian 13 virtual machine (Python port of run-debian13.sh)."""
+"""Start the Debian 13 virtual machine."""
 
 import os
 import platform