Allow Claude Code to be installed by default in sandbox images

[ryaneggz]

GitHub Issue Draft: Allow Claude Code to be installed by default

Title

Allow Claude Code to be installed by default in sandbox images

Description

Add support for installing Claude Code by default during sandbox image build or startup so new sandboxes include it without manual setup.

Motivation

• Reduces setup friction for new users
• Ensures a consistent baseline environment
• Makes sandboxes immediately usable for Claude Code workflows

Acceptance Criteria

• Claude Code is installed by default in the relevant sandbox image(s)
• Installation is documented in the sandbox README
• Existing sandbox behavior remains unchanged when the feature is disabled or unavailable
• Build and runtime checks pass after the change

Notes

• Review the current Dockerfile and entrypoint flow for the ubuntu sandbox
• Prefer a minimal change that preserves existing tool behavior
• If installation requires network access or auth, document the requirement clearly