feat: include ssh and scp in working containers

[kordless]

Problem

The nemesis8 working containers (used for run, interactive, and gateway-dispatched sessions) do not include ssh or scp. This means agents cannot:

• SSH into remote hosts to run commands or inspect state
• SCP files to/from remote machines
• Use git over SSH (only HTTPS works today)

This is a significant capability gap for any agentic workflow that involves remote infrastructure.

Proposed Fix

Add openssh-client to Dockerfile.base so both ssh and scp are available in all working containers:

RUN apt-get update && apt-get install -y --no-install-recommends \
    openssh-client \
  && rm -rf /var/lib/apt/lists/*

No server-side SSH needed — client only.