Refactor into npm package structure

[jeremyfelt]

Summary

Transform the current standalone tool into a proper npm package that can be installed as a dependency.

Tasks

• Update package.json for npm publishing (add bin, main, files fields)
• Create CLI entry point in bin/reglance.js
• Move core logic from root .mjs files to lib/ directory
• Set up proper module exports/imports
• Add package metadata (description, keywords, author, repository)
• Consider TypeScript conversion for better DX

Acceptance Criteria

• Package can be installed via npm install
• CLI commands work: npx reglance capture, npx reglance compare, npx reglance control
• Core functionality preserved during refactor

Current vs Target Structure

Current: capture.mjs, compare.mjs, control.mjs in root
Target: bin/reglance.js CLI + lib/ directory for core logic

[jeremyfelt]

Done in the v2.0.0 repackage (PR #37). package.json now has bin/files/engines and full metadata, the CLI lives in bin/reglance.mjs, and core logic moved into src/. Diverged from the original plan in two minor ways: code went to src/ (not lib/) as .mjs (not .js), and the optional TypeScript conversion was not pursued.