Add pattern generation and permutation counts

[KayleeWilliams]

Summary

• Add explicit category patterns for generated names, including a new city category.
• Add exported permutations() counting plus CLI --permutations and --json output.
• Refresh README documentation around quick start, patterns, CLI usage, counts, categories, and constraints.
• Update the permutation script to reuse the exported helper and preserve validator newline formatting.

Validation

• bun run validate
• bun run check
• bun test
• bun run build
• bun run permutations

Benchmark

Local source-module benchmark:

• joyful(): 100,000 ops in 11.64ms, about 8,589,620 ops/sec
• joyful pattern: 100,000 ops in 405.73ms, about 246,469 ops/sec
• permutations(): 1,000,000 ops in 22.21ms, about 45,032,197 ops/sec
• permutations pattern: 1,000,000 ops in 67.01ms, about 14,923,146 ops/sec