Expand Expression guidance and showcase richness checks

[changeroa]

Summary

• Add 54 unofficial brand studies, their hub and shared runtime, plus the original Hearth Clay showcase.
• Expand Expression with four directions, a study atlas, measured benchmarks and image/type/surface/product techniques.
• Update the creative build route and add optional richness checks for empty screens, transition density, masks and hairlines.
• Rework ten studies with drawn scenes and product surfaces; this is not a claim of faithful visual cloning or completion of the iyen.io redesign.

Verification

• Showcase checker self-test: 29/29 passed in the local session.
• The ten revised studies and Hearth Clay passed --richness error.
• Full showcase run: 55 passing results, one flex-team browser-closed error; isolated flex-team retry passed with exit 0.
• Domain validation (75 governed leaves), IA validation (154 leaves), material validation (180 admitted records), and staged whitespace check pass.
• Governance and matching domain/IA fixtures passed in the preceding verification session.
• Link validation has 163 existing failures outside the changed Expression/showcase/root routes; no related failures were reported. The entire repository link suite is not green.
• Ten trimmed videos and raw computed-style profiles remain local artifacts, not included in this PR.

Limits and follow-up

• Existing studies outside the revised ten still have richness warnings; warning-mode success does not mean the visual floor passes.
• Richness is a heuristic measured at desktop size, not a beauty score. Transition declarations do not prove meaningful state changes, and data-surface requires honest manual review.
• The checker currently uses a fixed 250ms sampling delay; deterministic reveal settling needs follow-up.
• New Expression files are navigable locally, but the closed material admission inventory remains 180.
• Original captures are historical evidence, not a claim that every live original was rechecked for this PR.

consumer_reference: consumer-reference/agent-native/registry.json