Prepare repository for public v1.0 release

[wmacomber]

Summary

• Prepare Phase 8A public documentation and repository readiness for eventual v1.0.0.
• Add curated screenshots, governance policies, community templates, ADR index/ADR 0010, changelog, and versioning policy.
• Add deterministic documentation and dependency-license verification, including distributed MIT and third-party notices.
• Align architecture, mathematics, sign-convention, testing, accessibility, security, and release documentation.

Repository settings

• Align description, homepage, topics, and private vulnerability reporting with documented policy.
• Protect main with required validate and review checks, up-to-date branches, resolved conversations, and force-push/deletion prevention.
• Use GitHub private abuse-reporting route for sensitive conduct reports because no maintainer mailbox exists.

Verification

• bun run ci — passed, including 207 Vitest tests.
• Full Playwright matrix — 206 passed, 47 expected skips.
• Pages-path offline test — passed.
• bun audit — no vulnerabilities.
• Reproducible build digest — 80c487ce672761782575bc6bd469786531a7aaf78d0cef381e64caf15576fa63.
• Live demo HTTPS smoke — HTTP 200.
• Documentation verification — 30 tracked Markdown files clean.
• git diff --check — passed.

Release tag and GitHub Release remain separate approval-controlled actions.