* fix: preserve access_control when cloning prompts
Cloned prompts now inherit the original prompt's access_control settings
instead of defaulting to null/public. This ensures that permission and
sharing restrictions are carried over with clones as expected.
If the original prompt doesn't have access_control set, defaults to {}
(private) which matches the behavior of newly created prompts.
Fixes#19360
* fix: clone access control
05a3aae59c