Adds the interactive HTML explainer for the feature-conformance enforcement
design, covering the four layers (TS brands, ESLint, boot assertion, CI gate),
manifest playground, mistake catalog, layer composition, build-order milestones,
anchor points in the repo, and an "extensions" section on sharper AST checks
and code-conventions enforcement.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
