Refresh README, docs, and Codex workflows

[TheSilkky]

Closes #369

Target base branch

• Base: develop
• Head: issue-369-refresh-readme-docs-codex-workflows-to-standard

Summary

• Refreshed README.md against the current Proofline README baseline while keeping server-specific scope, status, source-of-truth, public-claim, security, validation, and release/deployment details explicit.
• Updated server documentation to link project-wide governance, public voice, and README baseline claims back to the website source documents instead of duplicating that posture locally.
• Reviewed and refreshed reusable Codex workflow docs/prompts for current repo roles, base-branch discipline, docs-only validation, public-claim boundaries, and sensitive-data/key-custody guardrails.

Docs updated

• README.md, AGENTS.md, SECURITY.md, docs/README.md, and targeted docs under docs/.
• codex/README.md and current reusable prompts under codex/prompts/.
• Historical codex/archive/ and codex/work-orders/ prompts were not changed.

Website source documents inspected

• open-proofline/website/README.md
• open-proofline/website/docs/governance-and-political-alignment.md
• open-proofline/website/docs/repository-readme-baseline.md
• open-proofline/website/codex/README.md
• Relevant open-proofline/website/codex/prompts/* references

Validation

• scripts/check-markdown-links.py
• git diff --check
• git diff --check origin/develop...HEAD
• Verified the diff is Markdown-only.

Go validation was skipped because this PR changes documentation and prompt Markdown only.

Scope notes

• Revalidated against origin/develop before publication.
• No product behavior, API routes, auth/session behavior, deployment expansion, notifications, decryption, key escrow, playable export, or public admin/operator behavior changed.
• Key custody/decryption assumptions did not change; the PR preserves the current ciphertext-only backend guidance and explicit future-design boundaries.
• This PR remains draft until maintainer review.