`remote/session.py` — tmux session lifecycle (the run lock)

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Overview

A session.py module that manages the tmux session which is the run: create it detached, attach, report status, kill. The session is the lock — a live session means that script is busy, so there is no separate lockfile to go stale.

Complexity: Medium
Target branch: main

Context

• Session name ricecooker-<name>.
• Runs its tmux commands over ssh through transport.py (#704).
• Bookkeeping lives under .ricecooker-remote/ in the chef dir on the box; the exit code is written there when the command finishes.

The Change

• Model three states of a session: none, live, and finished-but-lingering.
• Identify a finished pane by the presence of .ricecooker-remote/exitcode, so nothing separate can go stale.
• Keep a finished pane readable with remain-on-exit rather than letting it vanish.
• Refuse to attach silently when stdin is not a TTY.

Out of Scope

• Deciding whether to attach or start fresh (driver.py orchestrates that from status).
• Building the command that runs inside the session, and its env (driver.py).

Acceptance Criteria

• Creates a detached session ricecooker-<name> running a supplied command, with remain-on-exit set.
• Status reports "no session" when none exists.
• Status reports a live session with its start time.
• Status reports a finished pane with its exit code, read from .ricecooker-remote/exitcode.
• Attach connects via transport's -t PTY form.
• Attach from non-TTY stdin refuses with a distinct exit code instead of silently attaching.
• Kill tears down the session and any lingering pane.

AI usage

Claude (Claude Code) drafted this from the design spec; I directed the design and reviewed it.