bug(cluster): cluster-entrypoint.sh fails with 'openssl: not found' #136

Bug

nemoclaw cluster admin deploy fails during cluster startup with:

/usr/local/bin/cluster-entrypoint.sh: line 255: openssl: not found

The container exits with code 127 (command not found).

Root Cause

Commit c6919aa (fix(security): harden sandbox SSH with mandatory HMAC secret..., #127) added openssl rand -hex 32 to cluster-entrypoint.sh to generate the SSH handshake secret, but did not add openssl as a package dependency in Dockerfile.cluster. The rancher/k3s base image does not include openssl.

Steps to Reproduce

1. Pull the latest cluster image (built from current main)
2. Run nemoclaw cluster admin deploy
3. Container exits immediately with exit code 127

Expected Behavior

The cluster should start successfully with a generated SSH handshake secret.

Fix

Add apk add --no-cache openssl to deploy/docker/Dockerfile.cluster.