- remove old CLI validation that only checked --pod flag
- add validation in namespaces.go to catch all paths (cli, quadlet, api)
- block userns mixing for all pods with infra, not just ipc/net
- update error message to be clearer
- fix test cleanup to use PodmanExitCleanly()
- use dynamic pod names in system tests to avoid conflicts
fixes#26848
Signed-off-by: 0xdvc <neilohene@gmail.com>