Store Uname from Tattach on each connection. Reject writes to
s/{id}/prompt when the connection's uname matches the target session
(self-prompt). Cross-agent prompting remains allowed.
Add ollie-9p-mount: a FUSE-to-9P proxy that attaches with a custom
uname derived from $OLLIE_SESSION_ID. Each session gets a transparent
mount — tools use ordinary file I/O and the identity is carried by the
underlying 9P connection.
Also adds a group registry (AddGroup/RemoveGroup/InGroup) on the server
for future access control use cases.
f9c9bc8969