Milestone 1 of SPEC.md. Zero-dependency Node server serving public/;
12-column tile grid with add (placeholder tile), drag to move, drag to
resize, remove; collision-free placement; layout autosaves to this
browser's localStorage and survives reload.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RNYUv9EyrGSFmCnmH7WYKH
