feat(cli): add initial CLI implementation with argument parsing and prompt handling

- Created package.json and package-lock.json for CLI package.
- Implemented argument parsing in args.ts to handle various flags and commands.
- Developed main CLI logic in cli.ts to execute commands and handle errors.
- Added configuration loading from a JSON file in config.ts, with environment variable support.
- Implemented prompt resolution and provider interaction in prompt.ts.
- Added usage documentation for the CLI.
- Configured TypeScript settings in tsconfig.json for the CLI package.
- Updated README in vscode package to reflect the new CLI functionality.
- Refactored root tsconfig.json to streamline project structure.

packages/vscode/README.md

@@ -1,4 +1,6 @@
-# LexAI — AI Writing & Code Assist
+# LexAI for VS Code / Cursor
+
+Part of the [LexAI monorepo](../../README.md) (`packages/vscode`). Twin of the [Chrome extension](../chrome/README.md) and [CLI Prompt Builder](../cli/README.md).
 
 **Bring your own LLM key.** LexAI helps you write and work with code in VS Code / Cursor — no LexAI account, no subscription, no LexAI servers.