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/cli/README.md

@@ -0,0 +1,88 @@
+# LexAI CLI — Prompt Builder
+
+Part of the [LexAI monorepo](../../README.md) (`packages/cli`). Complements the [Chrome](../chrome/README.md) and [VS Code](../vscode/README.md) packages.
+
+Improve a rough idea into a **paste-ready engineered prompt** before you fire it at Claude Code, Cursor, or another agent.
+
+BYO-LLM only — no LexAI servers. Uses the same Prompt Builder core as the Chrome and VS Code extensions.
+
+## Install (from this repo)
+
+```bash
+# from repo root
+npm run cli:install
+npm run cli:build
+
+# make `lexai` available on your PATH
+cd packages/cli && npm link
+```
+
+Or run without linking:
+
+```bash
+node packages/cli/out/cli.js prompt "your rough idea"
+```
+
+## Setup
+
+```powershell
+# PowerShell
+$env:LEXAI_API_KEY = "sk-..."
+$env:LEXAI_PROVIDER = "openai"   # optional: openai | anthropic | groq | openrouter
+$env:LEXAI_MODEL = "gpt-4o"      # optional
+```
+
+Optional defaults file (no API key allowed here): `~/.lexai/config.json`
+
+```json
+{
+  "provider": "openai",
+  "model": "gpt-4o",
+  "pattern": "role",
+  "persona": "Expert Developer",
+  "format": "Markdown",
+  "style": "Concise"
+}
+```
+
+Precedence: **flags > config file > env > defaults**. Key is always from `LEXAI_API_KEY`.
+
+## Usage
+
+```bash
+lexai prompt "add rate limiting to the express auth routes"
+
+echo "debug flaky playwright on CI" | lexai prompt --pattern role --persona "Expert Developer"
+
+lexai prompt -f draft.txt --format Markdown --model gpt-4o
+
+lexai prompt --list
+lexai prompt --help
+```
+
+The engineered prompt is written to **stdout** (pipe-safe). Progress and errors go to **stderr**.
+
+```powershell
+# Windows: copy to clipboard
+lexai prompt "write a unit test for parseConfig" | Set-Clipboard
+```
+
+### Flags
+
+| Flag | Meaning |
+| --- | --- |
+| `-f, --file <path>` | Read input from file |
+| `--pattern <id>` | Pattern id (`auto`, `role`, `cot`, …) — see `--list` |
+| `--persona <name\|text>` | Persona preset or free text |
+| `--format <name>` | Output format hint |
+| `--style <name>` | Style the engineered prompt should request |
+| `--provider` / `--model` | Provider overrides |
+| `-l, --list` | List patterns, personas, formats, styles |
+| `-h, --help` | Help |
+
+Exit codes: `0` success · `1` user/config error · `2` provider/network error
+
+## Scope
+
+**In:** Make Prompt / Prompt Builder only.  
+**Out:** Fix/Rephrase/Code Assist, reading VS Code/Chrome keys, auto-running shell commands.