v0.1.48

/dev/null self-heal (agent crash-loop guard)

An agent running with sudo (admin isolation) can clobber the shared /dev/null device node — e.g. tmux -S /dev/null treats it as a socket path and unlinks it — which then crash-loops every agent on the box (all writes to /dev/null hit EACCES/ENOENT).

• 5dive-agent-start now recreates /dev/null as the proper character device (mknod c 1 3 via sudo -n) before anything touches it. Guarded by [[ ! -c /dev/null ]], so it's a no-op on a healthy box.
• 5dive doctor gains a deps/devnull check that flags a non-char /dev/null and auto-repairs it under --repair.

Turns a fleet-wide outage into a self-correcting blip on the next agent restart. Smoke green (all rows).