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

seediso/debian13/README.md

@@ -1,7 +1,7 @@
 # Debian 13 seed.iso
 
 This directory contains the cloud-init NoCloud configuration used by
-`run-debian13.sh`.
+`run-debian13.py`.
 
 1. Edit `user-data`, `meta-data`, and (if needed) `network-config`.
 2. Build the image: