Use bash skills/spine-worktree/scripts/worktree.sh. A prototype is disposable evidence: name its question in the Session V2 artifact, never start a service while creating it, and promote only validated learning into normal work.

create <slug> --session <id> creates a normal implementation branch with an intact .scratch bridge. It bulk-carries only known useful ignored directories, currently node_modules, .svelte-kit, and .vite; arbitrary ignored paths need an explicit --carry <path>. create --prototype <slug> --session <id> enables filtered ignored carry-over for disposable evidence; secret-shaped paths and .worktree-skip entries stay denied by default. --include-sensitive <path> is an explicit per-create exception and prints only the path. Prototype carry-over filters every ignored descendant with NUL-safe path handling and denies symlinks by default. prototype-env requires a tracked .worktree-prototype-data-env declaration, reserves a loopback port, and writes a mode-0600 overlay with a worktree-local data target. The reservation remains held until prototype-env release <worktree> <session>; release it immediately before the project launcher binds the port.