Export built-in commands for composition

[boramuyar]

Summary

• export createBuiltinCommands from the public package entry point
• preserve the existing lazy-loading behavior and support selecting a subset by command name
• document and test wrapping a built-in as a custom command
• add a minor changeset

Motivation

Custom commands can override built-ins, but there is currently no supported way to delegate back to the original built-in implementation. Consumers that need to instrument a command or substitute part of its CommandContext must either construct a nested Bash instance or copy the command implementation.

This exposes the registry's existing lazy command factory under a public composition-oriented name, allowing consumers to decorate built-ins while retaining their implementation and execution context.

const [builtinCat] = createBuiltinCommands(["cat"]);
const cat = defineCommand("cat", (args, ctx) => builtinCat.execute(args, ctx));
const bash = new Bash({ customCommands: [cat] });

Validation

• focused registry and public API tests: 7 passed
• pnpm --filter just-bash typecheck
• pnpm --filter just-bash knip
• TypeScript declaration emit
• CJS and browser bundle builds, with runtime verification of the CJS export

[vercel]

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