stop automatically cloning user dotfiles to containers

[banksean]

Bare minimum:

• Replace with an explicit --dotfiles flag
• Create reasonable dotfile defaults

Or something more articulate like a Profile spec that defines the env, dotfiles etc for use in particular cases:

• One Profile for users, when they sand shell into a sandbox container
• One Profile for sand exec
• One Profile for specific agent types (interactive and oneshot might want different Profiles)

[banksean]

Fixed in 628e896