fix: validate negative deep option values

[abhu85]

Summary

This PR adds validation for the deep option to throw a TypeError when a negative value is provided.

Fixes #500

Problem

Currently, fast-glob accepts negative values for the deep option without any error or warning, even though negative depth doesn't make logical sense:

import fg from 'fast-glob';

const results = await fg('**/*.js', { 
  deep: -10,  // This is accepted but semantically invalid
  cwd: '.' 
});

This can lead to:

• Unexpected behavior in consuming code
• Unclear semantics (what does negative depth mean?)
• Potential bugs that are hard to track down

Solution

Add validation at the start of the Settings constructor to throw a TypeError when deep is negative:

if (options.deep !== undefined && options.deep < 0) {
  throw new TypeError(`options.deep must be a non-negative number, received: ${options.deep}`);
}

Test plan

• Added unit tests for negative deep values (-1, -10)
• Added tests confirming zero and positive values still work correctly
• Verified validation runs before other option processing

Notes

The build currently has a pre-existing issue with fdir and @types/picomatch dependencies (TS1259 error). The new tests follow the existing test patterns and were verified manually with ts-node.