Add Go utility functions package

[rjrodger]

Summary

This PR introduces a new Go utility package (util) that provides a collection of helper functions for common operations on maps, strings, and data structures. The package is a Go implementation of utility functions, likely ported from a TypeScript/JavaScript codebase.

Key Changes

• String manipulation functions:

  • Camelify() / CamelifySlice() - Convert kebab-case strings to PascalCase
  • Pinify() - Convert path slices to pin notation with alternating separators
  • Joins() - Join array elements with hierarchical separators

• Map/data traversal functions:

  • Dive() - Traverse nested maps to a specified depth, returning path-value pairs
  • Get() / GetPath() - Retrieve deeply nested values using dot-separated or slice paths
  • Entity() - Extract entity field validation from a model structure

• Data transformation functions:

  • Order() - Order and filter maps of items with support for sorting (alphabetical, human-readable), exclusion, and inclusion specs
  • Stringify() - Convert values to JSON strings
  • Decircular() - Create deep copies of nested structures

• Comprehensive test suite covering all functions with edge cases including nil handling, empty inputs, and complex nested structures

Notable Implementation Details

• Uses Go's strings.Builder for efficient string concatenation
• Implements custom integer-to-string conversion in toString() helper
• Supports hierarchical sorting with special markers (alpha$, human$) for flexible ordering
• Includes human-readable sorting that pads numeric strings for natural ordering (1, 2, 10 instead of 1, 10, 2)
• All functions handle nil/empty inputs gracefully

https://claude.ai/code/session_01FsVS8sfCXgTsFVVNE3vGvV