feat(cli): bootstrap CLI package structure — test script + src/lib module

[Copilot]

packages/cli was missing two structural elements called for in the bootstrap spec: a test script and a src/lib/ module directory.

Changes

• packages/cli/package.json — adds "test": "vitest run" alongside the existing dev script, completing the minimal scripts requirement
• packages/cli/src/lib/index.ts — creates the src/lib/ counterpart to src/commands/, exporting shared CLI utilities (apiBaseUrl, readCredentials, writeCredentials, clearCredentials, resolveInput, describeInput) from a single stable import path

// src/lib/index.ts
export { apiBaseUrl, readCredentials, writeCredentials, clearCredentials } from '../credentials.js';
export { resolveInput, describeInput } from '../input.js';