feat: show help for unknown flags and add showHelp function

[gaureshpai]

• Extract help message into reusable showHelp() function
• Show help when unknown flags are provided instead of treating them as paths
• Closes CLI treats flags as paths; should show help when no valid path is provided #77

Summary by CodeRabbit

• Bug Fixes
  • Improved command-line argument validation. The CLI now properly recognizes supported flags and displays usage information when invalid arguments are provided.

Confidence Score: 5/5

Safe to merge — the change is small, well-scoped, and the previously raised exit-code concern has been correctly resolved.

The PR makes a single-file change that correctly fixes the known issue. The exit code for unknown flags is now 1 (not 0), showHelp() is properly reused for the --help path, and no existing behaviour is broken. The only remaining note is a minor stdout/stderr mixing convention, which does not affect correctness.

No files require special attention.

Prompt To Fix All With AI

This is a comment left during a code review.
Path: src/create-next-quick.js
Line: 59-63

Comment:
**Help text written to stdout on error path**

When `showHelp()` is called from the unknown-flags error path, the usage information is printed to `stdout` (via `console.log`) while the preceding error message is printed to `stderr` (via `console.error`). Mixing streams for a single logical error response can cause output ordering issues when the caller redirects one stream, and it deviates from the convention that all output for an error condition belongs on `stderr`.

A lightweight fix is to pass a `stream` argument (defaulting to `process.stdout` for the `--help` path) or just inline `process.stderr.write` for the error case:

```js
const showHelp = (out = process.stdout) => {
  out.write(`
Usage: create-next-quick [project-name] [options]
...
`);
};

// --help path
showHelp();                  // prints to stdout

// unknown flags path
showHelp(process.stderr);    // prints to stderr
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (3): Last reviewed commit: "Merge branch 'fix/help-for-unknown-flags..." | Re-trigger Greptile}

[github-actions]

✅ CI/CD Test Results

Overall Status: success

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