Agent shell

A connected agent can open an interactive shell without exposing SSH or another inbound port on the machine:

$ graphenectl get agent
$ graphenectl agent shell edge-1

The terminal, resize events, and exit status travel through the installation's door and the agent's existing outbound session. The server authorizes the PTY request against the selected namespace before forwarding it.

The agent installation should set GRAPHENE_AGENT_PTY_USER to an unprivileged account. If the configured account cannot be resolved, opening the shell fails. An agent started as root without this setting warns and otherwise inherits that identity, so this setting is part of a secure installation rather than a UI preference.

The shell is an operator diagnostic path. Pipeline work should use typed activities through the SDK so its inputs, retry guarantee, ownership, and observability remain part of the run.