Phase-1 audits (feedback-behaviour, engine-surface, design/Manifold), the judge-panelled rl-feedback-design, dock/backends/inputs specs, the upstream-firmware survey, the Manifold design mirror, and BUILD-PLAN.md (resume anchor + locked decisions).
Source: archive/playground-redesign-2026-snapshot branch (commit 287e3a1). Reference-only — playground is being rewritten in SolidJS, so the redesign's implementation will not be merged, but its design intent is preserved here for the rewrite team.