docs: surface the design-partner program

[yhay81]

What changed

• add a direct design-partner section to the public homepage for ASGI, MCP/agent, and Workers workloads
• link directly to the bounded public application form and existing program details
• add responsive light/dark styling with reduced-motion behavior
• version the stylesheet asset to avoid stale production caches
• make the direct application link a generated-site regression contract

Why

Three owner-external applications remain a v1 evidence gate, but the application route was only visible deeper in the contribution and organization documentation. The homepage now exposes the real-workload path without weakening the program's privacy or independence requirements.

Impact

Visitors with a concrete application get one clear next action. The section uses the existing full-width visual system, has no analytics or new data collection, and leaves ordinary onboarding as the primary hero action.

Validation

• 15 pytest tests
• Ruff lint and format
• Zensical 0.0.51 strict build
• generated CSP headers and internal-link validation
• public PyPI release/pin freshness
• npm audit and pip-audit: no vulnerabilities
• zizmor: no findings
• light/dark text contrast: minimum 4.85:1 across new foreground/background pairs