v5.5.2

Fixed

• devcontainer.sh now skips system package updates that require sudo
• maybe_sudo gracefully handles containers with "no new privileges" flag
• zsh install skips chsh in devcontainers (shell managed by container)
• Clear error message when zsh not installed in devcontainer

Added

• is_devcontainer() helper detects VS Code devcontainers, Codespaces, and custom containers