Built-in skill — initialise a new CLAUDE.md file with codebase documentation. Shipped with Claude Code; usually the first skill any new repo invokes.
From Wikipedia
In Unix-like computer operating systems, init is the first user-space process started during booting of the operating system. Init is a daemon process that continues running until the system is shut down. It is the direct or indirect ancestor of all other processes and automatically adopts all orphaned processes. Init is started by the kernel during the booting process; in most Unix-like systems, a kernel panic will occur if the kernel is unable to start it or if it dies for any reason. Init is typically assigned process identifier 1.