refactor: Move recipe generator to cook/ directory and fix flattening bugs

- Move recipe-generator/ to cook/ for cleaner structure

- Fix ksflatten-relative path conversion to handle all %include paths

- Fix validation exit code to only fail on actual errors

- All recipes now generate and flatten successfully via make all

cook/ingredients/live/post/session.ks

@@ -0,0 +1,8 @@
+# Live session configuration
+
+%post --log=/mnt/sysimage/root/post-live-session.log # Beginning of the post-installation section. Add logging.
+
+# set livesys session type
+sed -i 's/^livesys_session=.*/livesys_session="gnome"/' /etc/sysconfig/livesys
+
+%end