fast-agent auto-activates its shell execute tool on any agent with
skills configured, and Context.no_shell — the only opt-out — has no
constructor or config knob. Add install_no_shell(), a wrapper on
fast_agent.context.initialize_context that stamps no_shell=True on
every context, installed from server.main() when the deployment's
agents.yaml sets a truthy top-level no_shell: key. Skill loading via
read_skill is unaffected. Default behaviour unchanged for deployments
without the key.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
