feat: add product marketing compositions

[0thernet]

Summary

Adds a product-neutral narrative and presentation grammar for Hraness technical-product sites.

• adds server-safe React compositions for outcome heroes, workflows, facts, installs, evidence, interfaces, trust boundaries, FAQs, and calls to action
• adds an independently importable responsive CSS contract with coarse-pointer and forced-color coverage
• documents the v0.3.0 public surface and adds a product-neutral gallery specimen
• verifies semantic headings, no-script rendering, public exports, package inventory, and accessibility media contracts

Focused verification

• bun test --preload ./scripts/register-stylex-test-transform.ts ./src/react/product-marketing.test.tsx ./src/product-marketing.test.ts ./src/react/design-gallery.test.tsx ./src/public-boundary.test.ts ./src/portfolio-inventory.test.ts
• bun run typecheck
• bun run lint
• git diff --check

The Required CI job owns the full build, package-smoke, complete unit, and headless-browser gate.