Cowork VM: add persistent package/setup mechanism across sessions

Summary

The Cowork VM is ephemeral — it resets between sessions. There is no mechanism to persistently install system packages (e.g. gh, jq, ripgrep) so they survive across sessions.

Problem

Any apt install or binary placement in the VM filesystem is lost when the session ends. This means:

• Tools like gh CLI are unavailable in the VM, forcing workarounds through MCP tools (e.g. Desktop Commander) to reach the host machine
• Users who rely on CLI tools for automation must re-install them every session or avoid the VM entirely
• The mounted workspace folder (/sessions/*/mnt/) persists, but there's no supported way to hook it into PATH or run a setup script on VM boot

Request

Add a persistent package/setup mechanism for Cowork VMs. Some options:

1. Startup script — A user-defined setup.sh (e.g. in .claude/) that runs on VM boot
2. Persistent bin directory — Map a workspace subfolder (e.g. .claude/bin/) into PATH automatically
3. Package manifest — A .claude/packages.txt that the VM auto-installs on boot (like a requirements.txt for apt)

Any of these would let users maintain a consistent tool environment across sessions.

Workaround

Currently, users can place Linux binaries in their mounted workspace and manually add them to PATH each session, but this is fragile and undocumented.