Add two subtests to virtiofs-misc that verify UID/GID ownership as seen from inside the guest: - uid_gid_mapping_preexisting: a file created on the host before VM boot must appear as root-owned in the guest. This acts as a regression test for issue described and fixed in PR #734. - uid_gid_mapping_chown: a newly created file is root-owned, chown to a non-root UID/GID is reflected in stat, and chown back to root works. The host side forwards KRUN_NO_UNSHARE into the guest environment; both subtests skip when the variable is set, since UID/GID mapping requires a user namespace on Linux. Assisted-by: OpenCode:claude-opus-4.6 Signed-off-by: Matej Hrica <mhrica@redhat.com>