Users and permissions: accounts, login, enforced file permissions, setuid, su, passwd, doas

The kernel now checks owner/group/other on open, create, unlink, rename, exec
and path search; honours set-user-id and set-group-id; restricts kill, mount,
reboot and mknod; keeps supplementary groups; and implements chown. devtmpfs
nodes carry owners and modes that chmod/chown keep. Terminals run login, the
image has root and schos, X starts as the ordinary user.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao

include/dev/pty.h

@@ -39,3 +39,4 @@ void pts_close(struct inode*);
 
 // From kernel/fs/devfs.c: the inode of master N.
 struct inode *devfs_pty_master(int n);
+void devfs_pty_claim(int n, uint uid);