Introducing a first-class `musafety sandbox` command makes the safer workflow
explicit: keep the visible repo on the base branch while creating isolated
agent worktrees for branch-local edits. Documentation, setup scaffolding, and
tests now reinforce this path and prevent accidental off-base sandbox starts.

Constraint: Sandbox creation must preserve current branch expectations for interactive maintainers
Rejected: Keep telling users to call agent-branch-start directly | it flips active branches and is easier to misuse in UI-driven workflows
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Keep README/AI setup prompts aligned with actual CLI commands whenever workflow commands change
Tested: npm test (38/38 passing)
Not-tested: Manual end-to-end run in a live VS Code multi-terminal session