* feat(cli): move flatten command to installer and update docs
Refactor the flatten command from tools/cli.js to tools/installer/bin/bmad.js for better integration. Add support for custom input directory and improve error handling. Update documentation in README.md and working-in-the-brownfield.md to reflect new command usage. Also clean up package-lock.json and add it to .gitignore.
* chore: update gitignore and add package-lock.json for installer tool
Remove package-lock.json from root gitignore since it's now needed for the installer tool
Add package-lock.json with dependencies for the bmad-method installer
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Co-authored-by: Devin Stagner <devin@blackstag.family>
