docs: add video product launch brand-kit example

[replynodes-ai]

Summary

• add one post-launch, non-blocking video product launch brand-context example
• document the exact scoped CLI command and six generated artifacts
• add a deterministic FRAME.md scene contract for title/intro, product, and CTA/end-card handoff

Boundaries

• documentation/design-only; no renderer, provider integration, CLI flag, dependency, test, or binary asset
• no invented brand data; missing signals remain unavailable
• logos and backdrops remain URL references only

Verification

• npm run smoke
• npm run package-shape
• node --check src/cli.mjs
• node --check bin/brand-kit.mjs
• node --check scripts/smoke.mjs
• markdown/example structure check
• git diff --check

Issue #564 was not resolvable through the public GitHub API, so this draft is intentionally not marked to auto-close it.

[replynodes-ai]

Independent architect readback for exact PR #5 head 64b96802e0bae7b781079fa4196ed2ed8a1af5fc: PASS.

Verified one post-launch video product-launch design example plus deterministic FRAME.md contract; exact scoped command, six artifacts, title/product/CTA scene bindings, unavailable/missing-data behavior, reference-only assets, no renderer/provider/flag/dependency/video output, and smoke/package/syntax/diff checks passed. No unit tests added.