feat(constructs): apply the 2026-08-25 library review [spec 0007]

feat(guide): public how-to guide + live AI model details

feat: make /product internal - lab members, maintainers, and PI only

feat: add welcome page for first-time users and update routing

Four-tier access model: self-governing admin, pre-login access, audit trail

Repro script: valid Python booleans + per-run filenames in instructions

Refine documentation and fix upload handling

Sync platform from lab mainline: dev instance ready to deploy

CCR Platform: web platform for Contextualized Construct Representations