Polish launch proof and contribution templates

[ardamoustafa1]

Summary

• Fix stale README/package launch metadata: version badge, Run 003 anchor, agent list, and eval-template links.
• Add an independent eval run template plus issue templates for third-party evals and showcase submissions.
• Update the launch playbook to reflect verified GitHub Pages status, the real social-preview dimensions, and the v2.1 next-release target.
• Tighten the PR template so proof/eval claims require raw outputs and local validation status.

Verification

• npm test — 13 passed, module check clean
• npm run validate — refs, a11y, and drift checks clean
• npm run check:links — clean
• Live Pages check: https://ardamoustafa1.github.io/DesignOS/website/ returned HTTP 200 on 2026-07-17
• Social preview asset check: https://ardamoustafa1.github.io/DesignOS/press/social-preview.png returned HTTP 200

Still requires GitHub Settings UI/API access

• Confirm repo description and topics match LAUNCH.md.
• Upload press/social-preview.png under Settings → Social preview if it is not already set.
• Confirm Discussions categories/pinned welcome post after Discussions is enabled.