fix: version-gate cgroup preflight check on openshell version

[ericksoa]

Supersedes #248.

Summary

• Version-gate the cgroup v2 preflight check: only run it for openshell < 0.0.8
• For openshell >= 0.0.8, skip the check (handled upstream via fix(bootstrap): use host cgroup namespace for gateway container OpenShell#329)
• Update error message to recommend upgrading openshell as the primary fix

Problem

PR #248 proposed removing the cgroup check entirely since OpenShell v0.0.8 handles it upstream. But users on older openshell versions (e.g. 0.0.6) would hit cryptic k3s failures on cgroup v2 hosts (Ubuntu 24.04, DGX Spark) with no guidance on how to fix it — we saw this today on an H100.

Fix

Parse openshell --version, compare against minimum 0.0.8. If older, run the existing checkCgroupConfig() check. If current, skip it.

Keeps bin/lib/preflight.js and test/preflight.test.js intact (PR #248 deleted them).

Test plan

• node --test test/preflight.test.js — 13/13 pass
• node -e "require('./bin/lib/onboard')" — no import errors
• Local openshell is 0.1.0 — cgroup check correctly skipped

[ericksoa]

Closing in favor of #248 — using the cgroup check removal as a forcing function to get users onto openshell v0.0.8+.